I can only orgasm if my butt is tight

You might have been ghosted, breadcrumbed, or paperclipped. You may not be trying to, but you're bordering on doing a kegel when you clench like that. A Look at Autism and Female Sexuality. Bend from the waist and use an overhand grip to grab one weight in each hand. Stimulating the pelvic nerve, via the rectum, can also lead to pleasure in some surprising ways. It helps to be really young, fit, and horny, something I haven't been for years.

Always use condoms. Become aroused before penetration. Make sure you really trust your partner. I masturbate differently than you, but it's still the only way I can get off.