What Causes Thick White Discharge And Itchiness In Vagina?

Hello,For the past couple of yrs. My vaginal discharge would always be white light on good days and thick and frequently off white on bad days no foul odor. I've been checked out at clinic they say I don't have any std as well as my boyfriend who's been my only sex partner for 5 1/2 yrs. also during sex my vagina has always been extremely dry for the past 3 yrs. recently this past week my discharge been so bad it was itchy and thick very very grit-like. I dug it out with my hand and it was just stuffed with discharge. I am currently using miconazole for this infection. a day before i used this cream there was slight foul smell and sight lower abdominal pain and when i dugg out discharge, the part closest to the opening of my vagina was pure white but at the base of my vaginal it had yellow hue. I don't know what to do past 3yrs I've been getting yearly check up since really started to have sex. First check up they gave me cream for vaginitis used the cream my vagina was good for about 6 months and went backt thick white discharge and every time Id get checkup since "There's nothing wrong there". So I'm very frustrated I just want to be healthy there again..what do you think the problems are and solutions to them????