Hi there - sorry to hear you are going through this. I hope that you have received some good guidance as you've tried to seek treatment, but here are my thoughts. If you are on the younger side, my concern would be about some underlying medical issue that could be causing your hair loss. Auto-immune conditions, various hormone issues (like your thyroid), or vitamin deficiencies (iron and others) are some of the common things to be looking into. Some require simply a blood test to diagnose, while others might need a biopsy taken by a dermatologist or hair specialist.
If you are older than 50 - 55, this may be related to menopause. And first it would be important to check your hormonal status with your primary care or OB physician to see if you might benefit from Hormone Replacement Therapy (HRT).
When it comes to hair transplant, the answer is Yes - with proper techniques and preparation, it is possible to transplant new hairs without permanently disrupting the hairs that are already there (your native hairs). This takes proper planning, making sure no other medical problems are present, and a skilled and highly experienced surgical team.
Hope that helps and happy to help anytime.