How did I get in this terrible position???

I’ve always been a very reliable and trustworthy person. Married a man I dated for 4 years and faithful for 27 years until my husband passed away. After that, dated men but one in particular for several years. Even though I love him I’ve looked for others on and off. Sometimes I dated others and we broke up and other times I still looked and went on dates even though we were "together". I couldn’t stop myself even though I hated myself for doing it. I can’t explain why other than I was looking for someone more financially compatible than the bf who only has a small amount saved retirement and a modestly paid job.

I’m ashamed but I can’t stop myself. I can’t go on like this. First I know it’s not right. Second my bf wants to live with me NOW and he wants to know I’m 100% committed but I can’t say I am if I’ve behaved like I’ve been, right?

Do you think it’s because I’m afraid it be alone and afraid to let go? Should I let him go and if I find the “right” person I wouldn’t feel this way? Maybe I can’t endure losing someone I love again so I’m avoiding commitment to either? Please reply if you have advice to offer and thanks.