Feeling unhappy during pregnancy

I'm 15 weeks pregnant, up till now I've been overcome with joy and me and my SO have been making plans for our house and baby's room, all our family are over the moon and I've been for my scans and felt nothing but love. 
This week I've been really sick and have had to take some time Off work cause every time I stand up I'm sick. I just feel hopeless and women at work kept making digs at me saying pregnancy is not an illness some women would kill to be you suck it up. 
It's making me feel like I don't deserve this and I'm going to be a crap mum, I'm getting angry at my BF for no reason and I just feel so unhappy it's scaring me. Has anyone else experienced anything similar? I don't know what to do to stop myself feeling so down I would appreciate advice