
Regarding birth control, as mentioned, the shot is very much russian roulette. Some women will have no trouble with it, others will have no end of issues. If you don't ever want kids, get a vasectomy. That is of course the safest option.
Second option is, try a different brand of condoms. Perhaps the brand you using just sucked or etc. There is a lot of difference between brands, believe me.
Edit, it's worth noting... I dunno if anyone else has this problem, but trojans are too goddamn small for me, it's like my best friend is getting suffocated. Lifestyles seem to be a much better fit.
I would advise staying away from trojans as in my experience, they're just too dang tight. I can't imagine that I'm the only one that has this problem with them.