If you have not missed a period it is unlikely that you are pregnant. But still for your confirmation get a pregnancy
test done. Regarding the brown discharge,as you said that you have fibroids and one of them being on the lining of the uterus
could be the reason for the discharge,depending on the size of the fibroid you need to take a call whether you want to get operated for them,with the age and the hormonal
changes there is a possibility that they may decrease in size but if it is bothering you much take a decision on whether to get operated or not.