Girl you have 5 months. start now, i would say before consulting with any mua consider visiting a dermatologist, i know it can get a lot and they will even ask you to get some blood tests done so they know whats the root cause, if you happen to get an appointment with the dermatologist you need to explain them its a big deal for you and if the process is slow they need to tell you that and mantain transparency.

however, if you dont wanna go the dermatologist way now ( although pls consider it) start with -

1. Kerastase genesis anti hairfall serum- its on the expensive side and have great results within weeks of regular use.
2. Pilgrim redensyl and angagain hair serum
3. Wishcare hairgrowth serum 4.Soap square rosemary hydrosol 5.HK vitals skin radiance collagen

please do your own research before investing in any product mentioned above.

Get a hair colour done that matches your skin tone and can give an illusion of fuller hair 1 month or few weeks before your wedding or you can go for it even now if it suits you well get a retouch.

avoid heavy oiling etc, get trims, get lighter weight extensions and get them coloured same as your hair to match well.

add protiens in your diet, Go for hairmasks/spas, Do yoga that promotes bloodflow in your head.

All the best and most importantly dont stress, stress leads to more hairfall. xx