Lump and odd stool?

[MartBP]

I recently bought a baby ball python (male) from a pet store. I can't be too sure of his age, as the pet store really didn't seem to know much about the snake (he was very small, likely barely out of the egg). A few days after buying him, he pooped, and his poop seemed like any other snake's poop. He seemed normal and acted normal as well, until recently. He did his business two times yesterday, and both times, they were a small brownish-yellowish piles mush along with a clear, slimy liquid (likely it's pee? Though I've never seen pee like that?). No brown or black, and no white. I noticed a lump near his anal area, and thought perhaps he was constipated. So I soaked him in warm water for a couple of minutes, until he finally pooped. His stool looked the same (yellowish-brownish mush and clear liquid), and his lump size decreased (he pooped quite alot that time). So I let him rest for the rest of the day. Today, when I checked on him, his lump had gotten bigger and more noticeable, and he was sitting above some of his own pee. So I let him sit in some warm water again, and a VERY small amount of white came out of his behind. I took him out, and I've been letting him rest. The bump doesn't feel hard or tough. Its soft and squishy, just as the rest of his underbelly would feel. Am I just overreacting or is this an actual issue?

Extra information: Maybe a week or two after buying him, I fed him a fuzzy mouse (previously frozen, but I thawed and warmed it up for the python). He seemed to eat it just fine. I feed him in a separate container. His actual enclosure is roomy. He has a water bowl to soak in, a hollowed half-log to hide in and help with shedding, and as a heat source, I'm using a heat lamp. I can't remember what type of bulb it has, but it's warm enough to keep the python warm. It has wood bedding (though I plan to change it soon. Please leave suggestions)