Who do you think you are to pregnant your ex?
You are selfish and self-centered. The only think you want is sex from her, and nothing else. Maybe in truth she doesn't like you enough to get into a serious relationship. She found out how irresponsible you are by your actions in which you intentionally not care about taking measures in birth control. Evidently, this is proved that you are selfish, irresponsible and not care about her emotionally and physically, so she is smart to dump you. You are just using her as a sex toy. Or maybe she don't have any others choice of better men so she go for you due to conveniencies.
You still don't understand why she dumped you?
Cuz you'are an annoyance, the reason you're there with her is for your own pleasure, sex, and this cause her to hate you. And fact that you're are there with her and the fact that she doesn't like that, infers she doesn't like you. If a woman likes a man, she wouldn't treat her man like that.