Depression during pregnancy?

im currently 31 weks preg with 2nd child and really get depressed i want this baby so much but my emotions are all over the place im crying all the time my husband is being so helpful but works long hours and i sit home long hours alone crying and feelin depressed my doc refuses anti depressants i can't go out much as i have bad sciatica and walkin at moment hurts 2 much im so weepy all the time is this normal as i didn't get this in 1st pregnancy i feel really down , we have no money worries and have a good relationship althou i feel i don't trust my hubby i feel very fat and uny and lonely and keep accusing him of cheating and not liking me please has anyone else experienced this im normally so outgoing and jolly but last few months i have felt like crap im snappy and moody and crying all time have no interest in anything