What Causes Weight Loss, Excessive Hair Loss And Missed Periods?

Hello doctor, I need some answers please. I recently had had a huge weight loss in a short period of time (26 kilos in three months) but I did not go through any surgery nor did I take any protein powder or any supplements (commercial wraps, pills, etc..) I just ate a lot of healthy food daily, drank lots of water and trained daily (did cardio+ high intensity interval training+ weight training) so I built lean muscle and toned my body while eating healthy food (lots of fruits, eggs, fish, meat, chicken, whole grains, raw nuts) But the things that are worrying me right now are two: 1) My hair started to fall abnormally since three weeks ago (after I ve started the maintenance phase) and whenever I d touch it, I would be catching a handful of hair, even when touching it successively, and even though I got a haircut, it still falls a lot. So some people started telling me that I should take multivitamins or iron pills, but I don t know what to do. Any advice? 2) I haven t had my period since 22 august, and that had me worried A LOT. I did experience the usual food cravings though when I thought it was time for the menstruation to begin last month, but today it s 3 November and I still didn t have my period. What should I do? Wait more or go see a doctor?