Spotting between periods and weight loss

I had regular cycles of period and for past 2 or 3 year having irregular cycle length .Some cycles are long as 51 days to even shorter cycle of 10 days.Also for past 3 cycles I'm having spotting before 3 or 4 days before periods..My last period started on 26 th January and lasted for 5 days.and on 14th(feb 8) 15th(feb9) and 16th day (today)of cycle found blackish brown discharge at first and then light brown around same time (4 30 pm). Is it normal? I suddenly lost 6 kgs without even trying.While trying to gain weight i lost 2 more kgs..I can't increase my weight even by eating more..As a result of weight loss I'm super tired .. Also I'm having heavy hairfall Is my irregular cycle related to hairfall and weight loss?