I'm isolating myself,staying silent. is this depression ?

First of all, you are never bothering people here, we answer questions like this because we want to help, or we have the same problems in common ( or once had them, and can give advice on how to fix it.) Second, overall I highly recommend that you do get someone to vent to, whether it's a therapist ( best choice) a friend you can trust, or a family member you feel comfortable with. Isolation only makes depression much worse. Unfortunately, you almost need to force yourself to be more social, even if it's just small steps at a time. If you are not sleeping, feel like a robot, don't feel like yourself for a while now, and cry a lot....you more than likely may need medication, depending on how serious the doctor or psychiatrist diagnoses your condition. Make an appointment asap, and always be as honest as possible if you truly want to fight this battle to regain the person you once were....the person you know you want to be again! I'll be honest, it's a long exhausting battle, that you need to just take ONE DAY AT A TIME! Also take into consideration that none of this is your fault, it's a disease like cancer that needs to be medically addressed soon. Lastly, be brave even on the worst of days...because depression may be different for everyone, but you can also learn how to control it with positive thinking and cognitive behavioral therapy. It works if you want it to, and stay committed to your recovery.