Discouraged while trying to bike...

So I fixed up my old bike with a new seat and cleaning it up. It works great, and Ive been hoping to do more after work to build up stamina so eventually I can start biking to and from work. I used to bike a lot as a teen so I thought it would be a great way to get myself more active again.

However, after biking a few times after work, the seat bent backwards cause I'm such a fatass and its really discouraged me. Ive managed to get it back into place but it feels like at any moment it can fall right back. It feels like a sign I'm too far gone. I've tried keeping my center of gravity more forward but it feels uncomfortable and makes my crotch feel weird or fall asleep.