Need Help

Hello. I'm 14 years old, and I just found this site when looking for a medical forum. Me and my mom are really concerned about my dad. He's been having some problems for some months now, and doctor visits haven't done him much good at this point.

So, I guess I'll just list off what he has and some other details. Sorry if I'm not being specific enough.
- Severe pains in abdominal and shoulder areas, possibly on leg.
- As of late, nausea and loss of appetite.
- When he gets home on the weekends, or even every night, all he does is sit on the couch in pain. He has a hard time moving. Before, he could move around a lot more than he is now.
- He's losing a lot of weight, possibly related to the loss of appetite?

And then there's one more thing. I have no idea if any of these symptoms are related to it, but a few months back my dad had a pretty good sized lump on his stomach, near the bottom. He saw a doctor about it, and they had no idea what it was and that was it. It went away later on, and now all you can see there is some mark if anything. Then, just a few weeks ago, my dad had a baseball sized lump on his shoulder. He got that checked out, and the doctors made him an appointment to get an X-ray and all this week. But now that lump is long gone, too.

I decided I should include some other things about him too.
- He does a lot of work. No, I don't just mean yard work. My dad has a sister and his mom who both always need help with something, and my dad needs to come to the rescue to fix it every time.
- I think he's a little bit stressed from work sometimes, he has very bad coworkers. I don't think it gets to him that much, though.
- He's 48 years old, is about 5'10, and weighs less than 200 pounds (as a result of the weight loss).

That's all I know to put here, but I hope it's enough. I really want to know what's wrong with him. I can't bear to see him in this pain.