Thanks for asking the query,Fluid filled blisters
on the lower lip are usually formed due to virsl infections certainly herpes infection. There are two types of herpes labial and genital herpes
the labial herpes are usually not transmitted by sexual intercourse although in some rare cases it can also spread by sexual intercourse.
Herpes is a acute viral infections in which fluid filled blisters are found on the lip and tongue which burst open and form ulcerations.
I would suggest you to maintain a good oral hygiene
take lukewarm saline rinses and antiseptic mouthwash rinses.
Consult a family Physician and get the checkup done for diagnosis and treatment plan.