Breastfeeding and delayed period

So I've been breastfeeding for 5 months now and after I had him I started my real period pretty quick. I started about a month in a half after I had him. But this month I'm 4 days late. I have had sex with my boyfriend but it's very rarely and we use condoms. Could it be stress and breastfeeding? Anyone else go through this or something similar? I just can't afford to be pregnant right now again cause I had a c section 😣