AIBU to think my husband has cheated?

[lovemycatmorethanmyhusband]

I really hope I am being unreasonable! Last night I found a small corner of a condom wrapper on the bathroom floor. Thought this was strange as we haven't used condoms for months (did have plenty left over.) so I looked in the bathroom bin and there was a used condom (hidden in a crisp packet!)

Confronted my husband straight away and he said he'd had a 'posh w**k' ie had used condom to masturbate. (Apologies for the frank language!) I let it go but can't stop thinking about it. AIBU to think he may have cheated? Really hope I am overreacting.

DH said that it is possible to get an STD if not using a condom whilst masturbating?

Does he eat crisps in the car? Hopefully it's all innocent but I'd be watching him like a hawk for a while. I've never known a grown man to have a "posh wank" but obviously that's not to say it doesn't happen. If you're together quite a while though and this is the first time he's mentioned posh wanking, then yes, I'd be a bit suspicious!

It's not something that often comes up in convo tho, is it?
How was your day, darling?
Splendid, oh light of my life. I had a posh wank and a packet of crisps.
Really darling? Out of curiosity, were they Walkers cheese and onion?