Pregnant with someone elses baby

Long story short weve been together for almost 2 years and we got in a huge fight and broke up for about a month and (fast forward 2 months and were engaged) BUT during that month i slept with another guy. (I know extremely stupid and immature and petty of me! I hate my entire existence right now for it! But i really was so mad and incredibly selfish. well now i just found out im pregnant and im pretty sure its the other guys baby and not my boyfriends😥😥😥 im so upset with myself and lost. Im so inlove with my boyfriend and i know hed be so excited about a baby but i just dont know what hes going to do when i tell him the baby isnt his☹️ i would be soooo devasted if he left again. Hes the love of my life and i could never have an abortion☹️ any advice. Anyone ever been in a similar situation?

*Im measuring 8.5wks