Pregnant again and devastated

I just had a baby 13 weeks ago and I just found out today that I'm pregnant again. I feel so stupid. I thought I could use breastfeeding as a means of birth control. I've been stressed with a colicky baby and fighting with my boyfriend so I was irresponsible. All I wanna do is cry. I finally lost all the baby weight and was getting back in shape to get back to being a personal trainer. I really hate myself and don't know what to do. I lnow it's my fault but damn, this is a crazy feeling still