Can I get pregnant this way?

So like I had sex on the 19th and on the 20th and it was unprotected and he cum inside of me. We did it many many times more than 3 times…anywayzz this app says I was suppose to get my period today. However, I haven’t gotten my period and I am very irregular so I didn’t think I was going to get my period. However, should I be worried? When we had sex I was cramping up the day before so I assumed my period was going to come but then it didn’t. I am very irregular like sometimes I don’t get my period but recently I’ve been having sharp quick pains on my left lower side and my back hurts and I have been having vagina cramps. I think this could be pms tho…any advice?