Advice? Please? What could this be?

I've been feeling not like myself at all. My symptoms include going from very depressed for a few weeks then being extremely happy and full of energy for 2-4 months then being depressed and suicidal again. I cry over nothing, especially at night. I'm very lonely yet I don't want to talk with anyone. I also have weird sleeping patters, I either need no sleep at all or I sleep all day and still feel tired. I'm restless and get very upset over little things. i get angry quite often, over the littlest things too. I'm always distracted and get obsessed with thoughts that I must do a certain thing, which makes it super hard to focus and do schoolwork or anything. I feel sad and empty a lot too. I think about suicide sometimes.I feel my friends are going to abandon me, I know it would never happen but I feel my friends would just leave me. I have really weird eating patterns. I only eat like 2 meals a day at most. I never wanna hang out with my friends anymore/ do anything fun. I just want to sleep and be alone even if I'm not tired. Then after 3-4 weeks of feeling like this, I feel like my normal happy/hyper self for 2-4 months then I'm depressed again? Thoughts?