This is a really hard one to answer because a "love hex" and a break up can seem like the same thing.
Usually the biggest indicator is a 100% complete turnaround. Meaning yesterday your lover was happy, loving, intimate, and fully in the relationship, and today they want absolutely nothing to do with you. When they leave, they remove all ties. They don't hate you... they just want nothing to do with you.
Now, before you (or any of my readers) think... OMG I've been love hexed... ask yourself these four questions:
1. Was the relationship really "happy" or were you just fooling yourself?
2. Was your partner really happy with you or were you just fooling yourself?
3. Was there a problem(s) in the relationship that just did not resolve itself?
4. Did your partner ever talk about breaking up and you talked them out of it?