You're still young, doesn't sound like you have dc together - get out while you can.
As for the decision not being easy - I was a married sahm to a 2 yr old living in a tied house (ex army) hundreds of miles from family, no support network, no income when I made the decision.
A cheaters script (google it) brief summary:
Gaslight (make other half think they're imagining things)
Lie
Deny
Get defensive
Minimise
Blame other half (not enough sex, nagging too much etc)
Dripfeed (it was only a kiss, ok it was 2 kisses...and a blow job...we only shagged once...ok maybe twice...)
Cry
Beg forgiveness (not all do this)
B - my first clue was mentionitis (ow name being mentioned more than other colleagues, always complimentary about her) then a man who had ALWAYS been a clock watcher, never volunteered for extra work etc was suddenly going in early, finishing late, organising socials (telling me it was someone else who had), working lunch times
If it's a pub/club night out why no partners?