Considering the fact that your snake is going to live 20+ years, if you're going to sweat weight gain and loss like you've been, you're going to drive yourself nuts!!! ... LOL ... Relax, snakes gain, snake lose, they are animals, don't try and "figure them out", just let them do their thing.

Blood around the cloaca is normal post shed. During the shedding process, skin is actually shed from inside the cloaca and there is sometimes a little blood when it's pulled out.

-adam