Friday night DP and I went out drinking. Came home, watched a bit of telly and then went to bed. We had sex and then fell asleep. I don't remember noticing anything weird at this point.
Early next morning, we're in bed and I notice a mark on his shoulder. It looked very much like a bite mark and I ask "wow look at that!! is it a bite mark??" and he said quite calmly "no, we were giving each other 'twisters' at work and it will be a bruise from that. But I noticed there was some more light bruising down his chest and on his arm.
As the hours went on, this mark starting getting worse - until it was an awful purple bruise massively resembling a bad, human bite mark. I questioned it again and this time he said "you did it, last night". No way!! I wasn't that drunk and I'm not a 'biter' anyway. So I protested and he said it wasn't the mark from the twister as it was obviously a bite mark and was too severe to be from the twister 
.
So, Sunday night we go out to watch a band and he brings it up again saying "you should see that mark you did now, it's bright purple" and he shows me it. I said "I did NOT do that, I would have remembered and I wouldn't have done it anyway" and he got quite defensive and said "well I didn't get it anywhere else!!" to which I replied "I never said you did but I didn't do it!". He followed this up with "I don't mind, I just wish you'd admit it" 
I keep thinking about it and it seems so odd!! It wasn't there when we first went to bed but I would have remembered doing it!!
So not to drip feed, it's a newish relationship and there have been a few slight signs of gaslighting. Not severe enough for me to say it definitely IS gaslighting, just a few hints (saying I've said things when I havn't) - the paranoid freak in me is wondering if he did it to himself and blamed me! I just can't see how else it could have happened!