My Boyfriend Cheated on Me So I Cheated Back But Now I Feel Guilty

So my boyfriend cheated on me with his old lover. He went out with her secretly behind my back, picked her up, they hung out, sent her back home, and this was going on for months all unbeknownst to me. I found out throught a mutual friend, I confronted my bf and he confessed, said that he had her as his lock screen (but as a joke?), said he chose her over me (but as a joke?), he also had two phones to keep talking to her behind my back but he swears nothing physical ever happened, I might be stupid but I believe him. Months go by and I thought I had forgiven him but I guess I held a bigger grudge than I noticed so I sexted my old talking stage and now I feel terrible. I

I thought I would feel fine because this was just me getting my lick back but my boyfriend said he never did anything physical or sexual withthe other girlso now Im thinking maybe I went a step further?

I feel genuinely awful and I regretted it so much, idk is my relationship lowkenuinely over? where do I go from here?