Is there something wrong with me?

I am 18 and about to start college. Sometimes I am very confident, talkative, and motivated, but sometimes I have no confidence in myself, am very shy, and I don't even want to get out of bed. My mom just calls me lazy and tells me I'm just making stupid excuses when I express these concerns, but I'm pretty sure it's something more serious. I know teenagers have mood swings and hormones make us crazy, but it happens all the time. There are months where I have no motivation to do anything at all. I don't want to get out of bed, I lay around the house all day, my family goes to the gym, but I just have no motivation to step out of the house or go work out. I have no confidence, I don't want to talk to anyone, I don't want to hang out with my friends, I just don't want to do anything. But then there are times where I do want to go work out and do stuff and a feel confident and like I'm worth something. I used to think it was just laziness I would outgrow, but as I get older, it stays the same and I really don't want to be like this anymore, but I just can't change myself.