Anybody have experience with calming ocd?

I've had and all my life but I am not currently seeing a doctor for it. I don't think I need to because most of the time I am fine, and I haven't see a doctor since I was 12, I'm 18 now. For the most part my life is normal, and it doesn't always affect me, but sometimes, I have 'episodes' I guess where I freak out and have to do everything at once. Usually it's cleaning or organizing something, and I will be physically shaking and feeling my heart rate go up even as I'm cleaning. There is no breaks, not even to eat or answer the phone. For example, today I came home from church and had an overwhelming feeling that everything needed to be cleaned. I started in the bedroom and I organized every drawer and cleaned everything, and then I went to clean my car (in the pouring rain), and then proceeded to spend six hours cleaning the entire house. I did not eat the entire day, I was hungry but I couldn't stop cleaning, and I missed three phone calls because I couldn't stop to answer the phone. After everything is completely clean and perfect, I feel better and go back to normal. So I was just kinda wondering if anybody has any experience with this? Should I just allow myself to keep cleaning until it's done or should I try to calm down and resist the compulsions? Also, sometimes thoughts get stuck in my head for weeks and it's the ONLY thing I can think about. And then the next week it's a different thought. For example: one time I thought I was pregnant because my stomach hurt, and the test was negative but I still thought I was and for that entire week, I was obsessed with the thought that I was pregnant. I thought of baby names and went to baby stores and took multiple pregnancy tests because I just KNEW that I was pregnant. And then it was just gone and I knew I wasn't pregnant and I didn't think about it anymore. And like if I apply for a job I'll be obsessed with thinking about working there. Like I'll look at pictures of their uniforms and plan what I'm going to wear to work and think about it constantly all day for at least a week.or I'll think of something dumb that I dos years ago and I won't be able to stop thinking about it and beating myself up about it for like the next week or so. And that happens with a bunch of different thoughts, but they're usually negative, so any advice about that is appreciated. Thanks (: