My ball python hatchling is swollen near the cloaca. it is also unusually sluggish when it moves.?

we just bought this ball about 4 days ago, it is my 2nd (other ball is over 1 yr). it was fine until today, just before the cloaca, it is swollen for about of an inch. a little bit ago, i noticed it moving as if trying to push excrement out. at the same time, it was waiving the tip of its tail. when i pick it up, almost the whole body goes limp, not try to wrap around my fingers at all. what could be the problem? i dont know if i should take it to the vet or not