Hi Haribo.
We talked a bit on your thread about his watch.
Physically and mentally, you won't be able to continue this. You've suspected his affair for months, you've been on high alert searching for clues and questioning him and then trying to hold it all together afterwards until the next time. You can't go on.
It's possible that he's having an affair. It's also possible that he's doing these things to wind you up - badly hidden chocolate bars with cheesy messages, cheesy keepsake cards with a woman's name on, a receipt... He could well be leaving things for you to find, and then acting like you're crazy when you mention them. The condoms, for example - they aren't used, they are almost bought for you to find.
They could be real, of course, but you'd imagine that if he was having an affair, he'd have stopped bringing keepsakes of the affair home as soon as he knew you were searching for things. He'd have hidden the keepsake better, and eaten the chocolate. He'd have left the condoms with her.
He leaves something for you to find, you find it, you accuse him, he denies it. He blames you for constantly causing arguments, and creates a horrible atmosphere. You don't like atmospheres, so you do what you can to give in to his demands and fix the atmosphere, and he rewards you when your behaviour is good by telling you he loves you or looking after you and generally behaving like a nicer man.
You need to stop looking for evidence now. Accept that this is over, whether he is having an affair or not, and that he will never admit it to you either way. Then seek legal advice. Find out what your overall position is on the house, make a plan for the future. Find a plan that lets you leave in a strong position but leave as soon as you can, because you simply can't take anymore.