I think you should wait a few years, but if your already messing with sarms then testosterone is a better option. Test will help you get bigger overall and make other anabolics like the sarms you have been using work better. You could probably get away with 250mg/week if you stacked it with rad 140. I'm only saying that option because you've already previously used rad140. Ditch the Osta, put the MK away for days you don't feel hungry.
I don't run test only anymore unless I'm on my TRT or cruising. But I use testosterone all year round.
Common sides at low doses are far and few, but being 19, I'd be looking for acne and gyno as possible, but 250+rad, I wouldn't expect issues.
Some people will say testosterone only but this isn't your first cycle you've already used sarms, and sarms are basically steroids. People like to act like they're not, but they are. Especially in muscle building doses.
Im also a rep for MaResearchchems, if your testosterone source doesn't have AI or HCG and SERMS, my screen name is a 15% off code at the website