As a fellow med student, I can tell you that the way you are feeling is normal. I'm just assuming you are in the US and planning on taking the USMLE. If so, everyone is stressed about that, I know I was. It's a sacrifice you have to make for the job you want. Yes, its stressful and time consuming, and in most cases, it leaves you zero time for socializing. If you are studying for step 1, its even worse cause you have to know a lot of theoretical knowledge you will probably never use as a doctor, and the exam is just so damn scary. I would like to say that it gets easier, but it really doesnt. I mean for me personally, I'm in clinical sciences so I enjoy it a lot more. Sure the hours are insane and I have pretty much no social life, but at least you are seeing patients and real cases. And the moment you finally see someone with one of those conditions that the USMLE loves to ask you about but you will probably never see in your life, it makes everything all worth it. I saw a guy with Redman Syndrome and another guy with Carcinoid Syndrome all in one day and I was like "OH SNAP!!!!".
That being said, just because it's supposed to be hard and time consuming doesnt mean you should be depressed. You need to find an outlet, force yourself to meet new people and to go out, or you will go crazy, I know I almost did. And don't be afraid to see a shrink. You, as a future doctor, should know that there is no shame in asking for help if you need it. My advice, pick a single day of the week were you just go out and have fun. My day was friday. After classes, I would meet up with my friends and we would go out and have fun. They Saturday and Sunday were study days. As for your confidence and all that stuff, you need to build it up, no one can help you with that. You just need to say to yourself "once a week, I'm gonna put myself out there and do something I would never normally do" and over time you will get used to it and build confidence.
P.S. Kaplan videos + First Aid + USMLE World = awesome Step 1 score!