I'm 20 and can't get pregnant?

It's already been 6 months I guess my timing is just off but it doesn't make no sense 😔 My boyfriend and I have been trying since March I know April I ovulated late and around May 20th that's when I got my period. I guess timing was off around that time. June and July I had weird bleeding but I guess it was just stupid Af but spotting and light bleeding on and off. I took a blood test for pregnancy on August 5th and it was negative. I had a faint faint + July 19 and my sister said I probably had a chemical? She had one too before but since I'm young my boyfriend tells me it should of been happen by now I'm really trying not to let this bother me and think positive it's just I hate waiting and waiting. Has anyone in their 20s took longer? I'm trying so hard to not stress!Â