Real SAT scores lower than practice tests-HELP

I took the SAT for the first time in March and got a 2040 (CR 620 M 680 W 740) and again in June and improved only 30 points 2070 (CR 640 M 680 W 750). My scores are incredibly inconsistent with my practice test scores (which range from 2190-2300). I have been prepping for months and have done a decent amount of practice tests; I have used CB’s online official sat course and the PR book. I don’t understand why I score so much lower when I take the real thing (other than being stressed). With fall of senior year approaching, I’m beginning to freak out–any tips or suggestions??