Cheating bf - what should I do ?

Well I've been dating my bf for abt 17 months & I love him more than anything . 2 months - abt 6 months he was cheating on me the hole time a lot & I didn't find out til months later . It hurt me so bad & I cried for a long time & I still cnt get over it /: I hate looking like an idiot & he made me look like a huge one but it's too hard for me to leAve him . I'm so insecure now & I still always think he's cheating even tho he swears he's not . It's too hard for me to trust him bcus when I actually did trust him , he hurt me bad . Wht should I do ?