You should undergo one blood test for beta-hCG to rule out pregnancy. It is more reliable than HPT.
Missed period may be due to hormonal imbalance, mental stress, over weight, irregular diet habit etc. Brown spotting
is related to late period itself, vaginal infection
etc. You need to take cyclic Progesterone
pill to regularize your period.
Kindly, consult with Gynecologist for complete prescription. Take healthy diet with IRON supplements
and control body weight.