relationship

well im 17 and i dont really know if i actually know what love is i have a girlfriend who ive been with for 13months we beeen through sooo much. we had gone out our freshman year but it wasnt workin but in that time she became my 1st kiss and she was all i really wanted after that, i didnt really go out with any girls i kissed girls at parties thats bout it. well after she broke up with a boyfriend she had we started talking again but i never really thought i could get her back ive never had too much self confidence ppl tell me im cute some even say i shuld be a model but thats only now that i grew my hair out, well my gf has cheated on me 2 times by kissing some guys but shes been honest bout it and she also flirted with guys. but after our 10 months of being together she started changin after cheating on me for the 2nd time. shes been really sweet and caring im really close to her family as she is to mine. but i cant seem to get over the past i think bout it oftenly and sometimes i even wonder if i should stay with her after everything. i feel like i get too emotional at times and hold onto the past. is high school love really something that doesnt last? is there anyway i can let go of the past shes showed me how much she regrets it she even cries wen she thinks bout how bad she hurt me i dont wanna lose her what can i do to let go of these memories?