I’m terrified

My mom has been trying to get me to take birth control, she knows my boyfriend and I have had sex and wants an extra precaution. We are very safe and always use protection. I have had a couple periods come a day or two late and scare me. We have slowed down on having sex because I simply don’t want to have that risk at all. My period was suppose to start over two days ago and I’m starting to get really worried. I’m only 19 and I don’t wanna even think about kids until at least 25. I wanted to slow down for this reason and he did too, but I’m afraid it’s too late. I feel stupid and I love my boyfriend and want this for him and I in the future.