I don't know what your doctor is like, and I'm certainly no physician, but I'd ask about a referral to an endocrinologist, just to find out if there's any underlying causes for the weight if you can't lose it through traditional diet/exercise.
If you have a thyroid condition for instance, a lot of GPs will just look at T4 numbers and only prescribe T4 medication. My wife has Hashimoto's and she has to take not just synthroid (T4 medication), but also liothyronine which is a T3 medication, and after her endo retired, she had a real hard time finding a GP that would prescribe her T3 medication. Many regular GPs don't understand T3 and are reluctant to prescribe any thyroid medication other than T4s.
My own experience, I went nearly 20 years thinking I had insomnia when it turns out, whole time I had severe delayed sleep phase disorder, which regular GPs generally don't know about. Well, insomnia medications don't work on DSPD, no medicines do... only thing that works for it is super intense light therapy that has to be done every day, forever and if you stop, your sleep cycle shifts back to where it was before. Now I don't do the therapy because it can only shift the rhythm by maybe 2 hours at best, which isn't worth the hassle and effort when that means you're only getting up at 11 am at best (a time still unacceptable by society).
But, even specialists can be bad. I also have schizophrenia, and the only medication, back when I was on meds, that worked for me at all was clozapine. At this time, I was taking meds to get stable, then getting off them until I needed them again. Well, I moved to a different state for a job and wasn't on meds, but the stress of the job was making me tank fast had to find a new psych doctor, found one and told him what I had been on, wouldn't prescribe it, insisted on risperidone (which I told him I had been on both risperidone and paliperidone and neither worked for me) because he "felt it was a superior medication".
Now I'm not saying you do have some kind of underlying condition or that your GP is wrong, but I'm of the philosophy of treating the disease rather than the symptoms whenever possible, and that's not to say a "weight loss drug" is a bad thing or shouldn't be taken, just rather I'd want to know if there was an underlying cause and if the cause itself could be treated.
