Hi, Welcome to HealthcareMagic Forum.
Your History suggests that you don't have any infection. The white deposits which you see after sex is nothing but the semen. If you happen to have a vaginal discharge
which may be of egg white consistency without any pain, burning sensation or foul smell, it is nothing but the normal cleansing process of the vagina which tries to clean itself and removes the impurities through the discharge. Kindly don't worry as it is not at all serious. You don't require medications and you can just leave a tampon inside your vagina when ever you have such discharge at anytime or after sex so that it absorbs it. But, if the discharge is foul smelling, it is a Infection, then you may want to get yourself examined by a Gynecologist. To avoid burning sensation after sex, ask your partner to increase the foreplay time to 20 minutes, so that vagina secretes more of lubricating fluid.
Good Luck, Take Care.