Where should I start
Hi OP, you can start by looking up "weightloss injections" and reading about them and how they work, then choosing which one to go for. I suggest this article might help get to the point quick enough.
https://onlinedoctor.asda.com/uk/wegovy-vs-mounjaro-vs-ozempic.html
Most here are on Mounjaro though so if you choose to go for it, you can read more about it.
is weight coming back after stoping injections ?
Yes and No. Weightloss injections are used in conjunction with proper diet (and exercise for those who're able to). Simply put, these injections help you to be consistent and stick to a calorie deficit which will help you lose weight. If you stop the injections and continue to stick to a calorie deficit, you will continue to lose weight or maintain your weightloss. If you stop the injections and start consuming more calories than you burn, you will start gaining weight, naturally.
There are other hormonal benefits to these injections which can also affect weightloss or weight gain. If you struggle with metabolic issues, then being on these injections may help 'fix' them which in turn will enable you to lose weight with a calorie deficit. If you come off the injections, your body may or may not work as well as if you were on them so you may or may not gain back some weight. Some people decide to stay on this medication longterm in order to continue treating these issues and maintain their weightloss.
If you decide to go for the injection, you can use this site www.monj.co.uk to find a list of reputable and GPhC-registered pharmacies to buy the injections from. You can buy from any provider from that list.
You can also check out threads on this Weightloss injections board and learn more about other people's weightloss journey, experiences, side effects and benefits. You can join any thread you want particularly December or January starter's thread where you'll find others like yourself who've just started or thinking of starting the weightloss medication.
Gearing up for a JANUARY start - weightloss injection
Mounjaro DECEMBER starters support thread - weightloss injections
Goodluck.