This thread answers the same question, but for a newylywed woman who is struggling with her husband’s past.
forums.catholic-questions.org/showthread.php?t=820806
I suggest reading the whole thing, seeking counseling, and thinking very seriously about this before moving forward. If you are going to hold this against your boyfriend for life, don’t marry him. Also, what does his practice of his faith look like? Is he doing it just for you, or would he go to church and go to confession even if you weren’t there? Once you had been married for some time, would he stop practicing his faith? In other respects, is he a good match? Does he have a good work ethic, can he support a family, do you have stuff in common besides being smitten with each other?
I also suggest reading the parable of the prodigal son again.
“Now his elder son was in the field; and as he came and drew near to the house, he heard music and dancing. 26 And he called one of the servants and asked what this meant. 27 And he said to him, ‘Your brother has come, and your father has killed the fatted calf, because he has received him safe and sound.’ 28 But he was angry and refused to go in. His father came out and entreated him, 29 but he answered his father, ‘Lo, these many years I have served you, and I never disobeyed your command; yet you never gave me a kid, that I might make merry with my friends. 30 But when this son of yours came, who has devoured your living with harlots, you killed for him the fatted calf!’”
Your boyfriend is kind of like the prodigal son, and you’re kind of like the elder son in the story.
“I still feel so nauseous just thinking about his sexual past as well as his past relationships because i don’t have any baggages from the past (first boyfriend) to give him and he has got nothing to complain or upset about.”
There are all sorts of different kinds of baggage: mental illness, phobias, quirks, physical illness, disability, addiction, bad habits, bad character (laziness, selfishness, being quick to anger, being unforgiving, etc.), weird family situations, bad credit, huge student loans, unfortunate genetic issues, etc. You and whoever you eventually marry will both have some sort of baggage. The only question is, what kind? I would really caution you to not focus on one kind of baggage, to the exclusion of all of the other kinds.