Light yellow discharge??

So I'm on the shot for about 3 weeks. Me and my bf are sexually active but since I've gotten on the shot my discharge has been very weird lately and this time me and my bf just had sex 2 times and he pulled out so after an hr or so I went to the bathroom and wiped and I have light yellow discharge it's not bright yellow just a tiny hint of yellow. It has a weird odor it doesn't stink it just smells odd. I've gotten tested for hiv and chlamydia and gonorrhea and I'm negative on hiv since I got the results right away but the other 2 my doctor said they'd call me in 2 weeks if it's positive and they never called back so I'm sure it's negative so what could it be?? Please let me know I'm very concerned