Questioning my sexuality

So I have always be attracted to men and men only. Last week I was watching a movie and there was an image of a naked women and I started thinking. Since then I constantly have thoughts about my sexuality every second of every day. I look at Instagram and test myself to see if I feel anything when I see pictures of women. It has gotten so bad that I have pretty much convinced myself that I am either bisexual or a lesbian. I feel like deep down I know I am straight and before these thoughts began to pile up I never thought about women before. Do you guys think since I am obsessing about it my mind is making me feel this way and as soon as I let the thoughts go I will relax or is my sexuality changing? Please help me