Why my website keywords are dropped day by day? can anyone help me please

Hi Folks.How are you? i need a big help from you guys. One of my website keyword rankings dropped from last months. I don't know why it’s happened like this. All of my website keywords are in first position from last 2 years. From last two months ago keywords are dropped 2nd to 3rd pages. I don't know the reason also. Spammed submissions also very less for my website. My Bounce Rate also very good. Daily I saw keyword positions in search engines, my competitors keywords are newly come to 1st in SERP. Even they didn't popular in search engines also. I never seen before and their traffic also very low. Please get me out of this problem guys...Please check details .one of My important keyword is “ Escorts in London " is in 40th position now. My website is completely related to escort related website