I'm not feeling good at all horrible lower back pain when should I go to the hospital for this it hurts comes and goes

go to labor and delivery. that's how I started going into labor when I had my sch. better safe then sorry

At only 21 weeks can I go to L&D like I can't stand up or sit down really it's so uncomfortable

And my stomach keeps tightening no blood or anything

I would still go in even if you're 21 weeks. If you're hesitant then call them and tell them what you're experiencing. But they'll most likely tell you to go in to monitor baby too

Please go. They are happy you are seeking help for both you and baby.