21 is a baby adult. Why not just enjoy the crush? It’s ok to crush on people. You can crush on multiple people at once. It’s sweet and cute. Please enjoy it, even if nothing comes of it. It’s a sweetness that will fade as you get older and life takes it’s turns. Others here made great suggestions. Ovulation just heightens things for us. As for intrusive/ compulsive thinking you can manage with a key word or with something like another thought, to train your brain into not going down whatever thought is troubling you. I use a keyword that stops me immediately. I have horrible intrusive thoughts that hinder me throughout my life. So I’m managing it with one word and it redirects me. It’s easier now with practice. Be gentle with yourself please