Facebook making me depress?

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I wanted to delete facebook account but due to I have many friends and relatives in facebook and I use facebook to contact them therefore i didn't do so. The reason that I want to delete facebook is because broke up with my ex and everyday see her online in fb(I don't want to block her because that will show me not being a man) , and saw her with a guy(I am not sure whether is he her new boyfriend or just friend). Now I am abit of sad (i guess) and down. Am I being jealous or just sad? What should I do? I can even sleep at night.