Looking for advice on weight gain

Hi so I’ve never posted on here but I’m looking for some advice if anyone could please help.

I am 23f and I have a really fast metabolism to the point where I’m now struggling to put weight on and eat. I currently weigh 90 lbs (6 stone) and I’m 4ft 11. I’ve always been a gym girlie and quite active, I work out between 4-5 times a week for 30-45 minutes as that’s all my body needs to stay in shape but Im still struggling to put weight on and at this point the gym is just making me waste away as there’s nothing to build on I’m just currently bone and muscle. If anyone could help me and tell me like what the most effective way for me to put weight on or what type of foods to eat or just some sort of help please I’d appreciate it♥️

Thanks for reading x