Vaginal itching and burning after having a lot of sex. what is causing it? could it be a yeast infection? how do i treat it?

Maybe: "A lot of sex" may cause friction injury to delicate vaginal lining. Also spermicide or lubricant on condom may be irritating. Trichomonas, an STD, may do this. Regardless, sounds like it's time for a break to allow things to cool down. If symptoms persist or you have discharge, see a healthcare provider. And avoid risky sex to prevent infertility and/or life-threatening STDs.

Yes: it can be a yeast infection or a dry vagina with skin irritation See your provider for an exam and to provide the right therapy

Try condom: The vaginal vault could be too dry and rubbing would result in itching and burning. Semen may be the trigger altering your vagina’s chemistry. Other possible triggers are lowered immune resistance, douching, birth control pills, antibiotics, or cuts, abrasions, or other vaginal irritation (friction from intercourse, fingers or fingernails, or tampons). You might try a lubricated condom.