I am a teenager and im confused with whether i may be depressed or not and if i have had it before.

My upbringing so far hasn't been that great, my dad stopped all contact when i was 6 and my mum remarried to an abusive man, however she divorced him 3 years ago. I haven't heard from my real father until 9 months ago when he contacted me and my siblings for the first time in over ten years. He contacted us through a social network site but we haven't met face to face. I was confused about why he left and had all these questions which he wouldnt answer. He also was being a bit too forward in the way of trying to instantly be my father again and it just felt so uncomfortable. During the three months after he first came back in contact i was not myself. Constantly crying, always at a low point, having dark thoughts and i self harmed. After 3 months i thought i can't carry on like this so i told him to just not contact me and i stopped all contact with him 5 or 6 months ago. He is still in contact with my siblings. It helped at first, i became happier but then recently i have been really overly emotional and feeling down again, i'm also confused with whether it may be because of that because sometimes i get down about nothing. I feel really emotionaly and physically drained and i have just finished my exams. I'm not sure if this is depression or not and if i had it before?