Stop flapping! I know it's not great, but look around you: Very few woman are rendered bald because of this type of hairloss. I'm not sure you should resort to a hair topper just yet, although I think it's a good idea purchase one as a back up, so you know that if other methods don't work, it is there, so your hair can still look great.
You could re-consider HRT, or the contraceptive pill. This is fairly drastic, but as PP have said, you don't have to wait for periods to cease completely before starting HRT. This may need a change of GP
Your iron levels could be higher. You can buy 200mg ferrous sulphate OTC from a pharmacist, or floradix from boots or superdrug. Take with vitamin C. If you go for the (cheaper) ferrous sulphate, be aware that they are very dangerous for young children to ingest. If you eat eggs, the yolks are high in iron. You should also take a hair supplement. Viviscal is meant to be amazing, but is extremely expensive. Perfectil is a lot cheaper. Holland and Barratt always have it on 3 for 2, always have an online percentage discount, give you points and free delivery if you buy enough packs.
As a pescatarian, make more of your fish oily. So good for hair and skin (and heart health)
Topical applications can be very helpful: grow gorgeous serum, ordinary density serum, minoxidl. I am personally doubtful about the efficacy of shampoos and conditioners to promote growth, but they can definitely improve the thickness of your hair
Wash your hair often: This does not make more hair fall out, keeps the follicles clean and stops roots going flat and greasy
Hairstyle: If you have a lot of length/thickness as the back of your hair, the sparseness at the front will be made more obvious by the difference between front and back. (Think balding man with ponytail, kidding himself that he has youthful hair). You may want to remove some of the length or go for a more balanced hairstyle, that minimises the difference in hair density across the head. You may need to grow out a fringe, or even cut one in