Cherlie, I'd like to think I know you pretty well... as much as you want to hear encouraging advice from all of us, I cant give it to you.
There are numerous problems that I see (because Ive experienced them) that will NOT change.
1.) Insecurity. You mention that she was diddlying around on you at some point. Was this before you married her? During? In any event, she will do it again, sorry. In addition, the reason she is accusing you of screwing around behind her back is because either A.) She knows how easy it was to do when she did it, or B.) She knows how easy it IS to do when she IS doing it.
2.) Lazy/Insulting behavior - This CAN change. As far as Im concerned, the duties in a marraige (or any serious relationship) should be split 50/50. It seems like this one is about 100/0. She needs to get a job, cook dinner instead of watching TV, and clean the fluff'n house up. This is not a sexist statement, if she was working two jobs, I would expect you to clean the fluff'n house and cook dinner.
3.) Age - She is 18 years old. She thinks she knows what she wants. She doesnt. Use your imagination and figure out how she is going to test what she likes. Get rid of her before she does it.
4.) Sex - Sexual ability has alot to do with attitude - not experience. If a girl sucks in bed when shes 18, shes going to suck in bed when shes 40. Does she have any insecurities about her body? Something that wont allow her to loose her inibitions? I dated a girl like this once... it was fluff'n horrible. People underestimate how important sex is in a relationship. Anyone who tells you any different and tries to seperate the emotional from the physical has watched too many Dr. Phil episodes and has no idea what he's/she's talking about.
Overall, in a nutshell, it sounds to me like youve made up you mind to leave. Better to do it sooner than later. I say start packing your bags.
Catch me what Im online sometime - we'll shoot the toejam about this.