Parasite? I have always bee fairly skinny and had a hard time gaining weight. I recently spent a few years in the Philippines. I heard you could easily get parasites over there. I didn't think much of it but I've been back in the US for a year now. In that time I've been trying to gain weight by eating about 3-4000 calories per day and working out every day. I gained about 10-15 pounds in 6 months and then got busy with work and stopped working out. Since then I lost a bunch of the weight I had gained while maintaining the same high diet. My mom is worried that I might have gotten a tape worm or something like it in the Philippines and it is making it more difficult to gain weight. I have no abdominal pain and haven't been sick since being home. Could this still be a possibility?

A very slim chance, normally if there are such things it will be very very obvious with other health issues. I had a problem after being in South American jungles, but there was no way to not know.

With that said, of course there could be other infections or problems, no one here may know, and no one will know without a proper medical exam. Let the doctor know about your ovresea trip