A private investigator has revealed the 12 warning signs to watch out for if you believe your partner is cheating.
The private detective, who offered his advice on the condition of anonymity, released the guide to help women gather the evidence they need to put their mind at ease - or to confront their partner over their infidelity, the Daily Mail reports.
From the slightest change in the position of the car's passenger seat, to an interest in a new hobby, the signs can often be far subtler than lipstick on a shirt collar.
The online guide, released today, was created in collaboration with business listings site Bark.com after it saw a 39 per cent increase in demand for private investigators.
For those who need the final piece of evidence to confirm their suspicions, the private investigator has provided five 'tests' that can be carried out to reveal a partner's true feelings. He also shared a five-step plan to confronting a suspected cheater.
Fear your relationship might be in jeopardy? Scroll down to find out more...
The 12 warning signs of infidelity
1. They are playing new music
If your partner is spending time with a new person, it makes sense that they would pick up on some of their interests.
A sudden interest in a genre or artist who previously didn't get played might just be a sign that he's mirroring someone else's taste in music
2. The passenger seat has been adjusted
If the car's passenger seat has been moved, it shows that someone else has been riding shotgun with your partner.
Moving the seat back is likely to be something that he would forget to do if he was covering his tracks.
3. More mileage on the car than there should be
Where has your partner been going that requires extra mileage? Everyone has a standard mileage they do each year, travelling to and from work, going on trips etc but if you don't know where your spouse has been going, it's a big warning sign.
4. Being protective of phone, social media or email
This highlights that there's something to hide on these devices. They may also take their phone to the bathroom, keep it on silent or always keep it face down. Any calls are taken in a different room.
5. Dramatic change in sex drive
This could mean that there's more or less sex in the relationship. The partner could feel guilty for cheating, so wants to cover it up by initiating or avoiding sex because they're getting it elsewhere.
6. Decline in communication
This could be little things, such as what happened in their day that they used to share and no longer do, or big things like refusing to discuss the future.
7. New clothes and underwear
If new clothes and/or underwear have been purchased, which is unusual in the relationship, it may be that they are wearing it for someone else and making more of an effort.
8. Change in personality
A change in personality is a big sign of infidelity, it could be that they're being more secretive, more argumentative and less affectionate. Sometimes it's as a result of guilt, but it could also be the influence of the person they're cheating with rubbing off on them.
9. They want to do their own laundry
They want to do their own laundry – they don't want you looking through their pockets, seeing any potential lipstick marks or smelling any different scents, such as perfume or aftershave that is not yours.
10. They start using new phrases
This indicates that they've been around someone a lot, who has influenced them. Your partner then begins to pick up their habits and phrases.
11. They're spending more money
They're spending more money – they could be spending money on clothes, hotels, gifts for the person they're cheating on you with, if it's unusual behaviour, you should find out where this money is going.
12. You catch them not wearing their wedding ring
You catch them not wearing their wedding ring – this shows that they don't want to appear to be in a committed relationship and are hiding your marriage from others.
Five 'tests' to set your partner if you suspect they're being unfaithful
Having a heart-to-heart is always the best option, but if you don't think they are being honest with you there are some tests you can set to look for evidence.
1. The body language test
Show up at their work at lunchtime and see what their reaction is. Are they rushing through, distracted, uncomfortable?
2. The phone test
Get a mutual friend or family member to call your spouse, chat to them and then ask to speak to you.
You then walk around and leave the room to talk to them, and whilst you're out of the room, you can quickly check their phone: so texts, calls and emails. But you have to make sure that your partner is on their phone at the time so it'll be unlocked.
3. Their location
Download a phone-finding app, such as 'Find my phone' on their phone, call them when they're out and check to see if where they say they are is true or not. If they are at a different place to what they tell you, investigate!
4. Get an STI test
Get yourself an STI test if you're sexually active with them. If you're not, wait until they go to the bathroom and before they flush, shout urgently for them to come to you. This would distract them enough to not flush the toilet, which you can then take a urine sample out of and send off for an STI test.
If they come home late and you think this is when they've been cheating, rush up to them as soon as they walk in the door. You can kiss or hug them and try to detect any unusual scents and check their pockets. If your spouse tries to push you away, they feel guilty and it may be time to look for any suspicious receipts, phone bills or bank statements.
How to confront your partner if you suspect they are cheating
1. Have real evidence but respect their privacy – you can't take back the accusation once you've made it, so it's best to be as sure as possible
2. Think about what you're going to say to your partner beforehand
3. Think about what you want to happen if it's true and if it's not true
4. Calmly confront your partner and discuss why you suspect they're cheating
5. Calmly discuss what you should do next in your relationship