Help me std?

Me and my boyfriend had sex for the first time in March of this year. Since then we've had sex protected and unprotected. It is now July, and the last time we had sex, I bled afterwards. I thought that was very strange but I have not told him. Now I have horrible lower back pain and cramps for almost 5 days. Can't be period because I'm in the middle of my cycle... Idk if i should tell him my concerns because I dont want him to freak out and also im broke and to get tested costs 50 ... What do i do..