Breaking up w/ bf of 5 years

I honestly need advice I'm 21 and I've been with my boyfriend for 5 years. In the beginning everything was good and now he can't keep his word for anything and he doesn't do anything to keep me anymore. In my eyes I feel like he could careless if we are together or not. And I know those are red flags to leave but it's super hard. He is all I know. Please if you have been with someone for a long time and you guys broke up how did you deal with it? I seriously need advice. We go to school together, and the same major (we didn't chose together I swear, we just both enjoy the same thing) anyway please give me advice on how to move on. Thank you 💜