could it be postnatal depression?!

Hi i was just wondering if anyone could help me, i had my first baby 8 months ago and since then i have felt really down, but only recently thought there might be something wrong, basically i'm really teary all the time for no reason at all and the slightest thing can set me off, i'm so easily wound up and it keeps causing arguments with my partner, at the time i think i'm justified in what im saying but afterwards i can see that i am completely overreacting, i hardly ever see my friends anymore and i feel really lonely, i'm not motivated to go anywhere or do anything and just feel like my life has stopped, also it takes me around an hour to get to sleep every night while i just run through things in my mind but i can't remember if it has always been like this. my little boy is gorgeous and i feel no resentment to him whatsoever, in fact he is the only one i don't feel any resentment too. I also suffer from frequent headaches. I'm also worried that if i go to my Dr. he will tell social services? and as i said before there is no problem with the way i am able to look after my son.. does anyone know what he would say or if he would prescribe me anti depressants? Any advice appreciated thank you :)