Another baby, big problems?

I had a baby girl when I was 16 with my high school boyfriend. We were together for a few years, but things just didn't work out, we were different people and wanted different things. My daughter is 4 now and her dad is married, has two kids that aren't biologically his, that are the same age as my daughter, and they're having a baby that's due in two months. she's having trouble adjusting and we're working it out at both households. My husband and I got married last month and want to try for a baby next year but I'm very hesitant because my daughter goes to her dads house every other weekend and sometimes goes on vacations with them. I'm worried that when we have a child he/she will be confused/jealous of my oldest because she'll be going different places and getting the extra gifts at Christmas and having different experiences. I don't want either of the children to pick on each other or have less or more than the other. Should I just not ever have another child? I'm so worried.