Help or recommendations?

When I had my son, I started getting really anxious about his Health and started to really worry about death and what would I do if my son or SO passed away, or what they would do if I passed away.  I thought it was just normal thoughts but it started It started to be on my mind all the time and it has subsided a bit but not very much and I can not seem to find a way to cope with these thoughts.  I've talked to my doctor and was put on a low dose antidepressant and that help a little bit but I had to Be taken off them when I found out I was pregnant again.