I just read your other post, where you mention that you tested negative for herpes. I don't know when your most recent exposure was, but if you've had no possible exposures within the last 4 months, you can safely say this isn't herpes.
It doesn't sound like herpes. Herpes is usually a cluster of blisters, not something spread out over your lips in a straight line. I'd wonder if you are having an allergic reaction to something you are using on your lips (a new chapstick, for example) or something you are eating or drinking.
If you have follow up questions, please keep them to one thread. It's hard to help you as well as we can if your information is spread out in different places.