Talk it over with her and tell her you don’t feel like you took the time you really needed between the relationships and you regret it. Let her know you still like her and everything, but you don’t think you’ll be able to get over this issue unless you take a break and fully process being alone. But you can’t expect her to wait patiently on you while you discover yourself. And there’s no guarantee you’ll still be interested in her after you’ve spent some time alone. You may just decide you like alone time, or maybe you wanna move, or do a job that keeps you away, or maybe even you’ll decide that you’re wants don’t align with what she wants.

So make this decision being prepared to not be with her anymore. Breaks can ruin a relationship, or they can make it stronger. But make sure this is something that would truly be good for you (which, after a long relationship, I think it would), or if this is just your head telling you these what-ifs.