Just found out Im pregnant Please Help!?

I just found out that Im pregnant. I decided to take a test after My Husband points out that I haven't had a period lately. So I looked on the calender and My last period was July 10. So I take a test. Comes back positive. Now im so stressed because I don't know if My baby has been getting the right nutrition it needs. I haven't really been eating at all for the past few months and I have lost weight. Every time I actually had time to eat, it would be fast food or something quick. ld even eat. Some days, I just wouldn't eat at all. I didn't know I was pregnant so I didn't take prenatals. I just started going back to college in August and around the same time I started a new job! I already have 3 kids so you could imagine how easy it is for me not te have time to eat. But one of My biggest concerns is how have I affected my baby in these past few months? I know I cant go back and fix it now but I am highly concerned that I have already done damage. I don't smoke or drink so I haven't put any poisons in my body. I just went out and bought Prenatals. Please just someone explain to some things that I need to worry about now. Should I even worry at all? I just had a bab 6 in a half months ago. So I don't think my body was completely ready for a new baby. UGH!!!! Im stressed! Some help!