Hey, it seems like you're just under a lot of stress right now. If you try to show your friends that you're sorry for any bad moods you may be having, I'm sure they'd understand and try to help you get through this. We can't be happy all the time after all! Think for a second. Since you've start school, have you been focusing more on schoolwork and less on things you enjoy? Even though it's important that you're working hard, you need to take a breather and do things that are carefree. You need to relax from time to time. If your schedule is too draining, you might want to consider talking to a counselor to try and lighten your courseload.
Are you getting enough sleep? Sometimes, in these situations, we work too hard and don't get enough rest. Rest is important because it's during this time that our bodies repair themselves and, if you're not getting enough sleep, your feelings of stress will keep piling up. Try to set aside time to go to sleep instead of doing other things that might be killing your time.
As I've said, I think it's important that you talk to a counselor to get things straight. You're obviously going through some issues right now and you should set yourself on the right track. You've been happy in the past so you know you can be better but you just need to make that effort to help yourself! There are a lot of people out there that want you to feel good so go for it!
I hope this advice helps. I know life can be tough sometimes but try to do what you enjoy and also try to talk about your problems. Just getting things off of your chest is sometimes the best medicine. I'm sure you'll make it through and be stronger in the end. If you have any more questions, feel free to message me!
Stay strong!