Most Helpful Girl
Gosh how long have you been seeing her and did she ask if you are exclusive? This kind of thing can really mess a person up. You should have at the very least told her when you started sleeping together.
If you guys have been involved for more than a month or so I'd say your only options at this point if you wish to avoid breaking her heart is to stop seeing other women now or break up with her. Telling her is not an option in my opinion and will only make it worse. I'd rather think you lost interest than find out you betrayed my trust.