PP Dreams

I'm about 7 weeks pp. I exclusively breastfeed but didn't wait the 6 weeks to wait to have sex. SO and I did it at 5 weeks pp and I started my period right after that. I know it's not very likely for me to get pregnant because of the breastfeeding and all but I'm so worried about having another baby. Not because we're not financially stable but because I want to go back to school and start my career so I can be ready for another in like 5-6 years. I just started on the pill a week ago and am considering an IUD but I've been told you need to be on your period to have it inserted and my insurance ends at the end of the month. I've started having dreams where I'm pregnant or my SO cheats on me and gets another woman pregnant. Is it a sign that I'm pregnant or just stressing too much?