Welcome
I think the guys are right dude. You gotta stay focussed remember many of us here are quite a bit older and experienced and they have shown their concern and voiced their opinion.
Tough love, yeah, there will be some, but I'd say never...ever throw in the towel that's just not the way.
Have patience...after all when you said you were vomiting, and had a high fever, well then you should not be surprised that you have lost weight, unfortunatelly our bodies can throw away quicker than they can build but...most things in life are like that.
Think of ants...and bees...man they just never, ever give up! HST is a great way to train and to me is a recipe for life, simply because you train smarter...not just hard all the time with no end result!
keep up the work and maybe switch to a simplify and win routine, I'm surprised Lol didn't tell you that already, if you don't want to gain too much fat, stay on about 500 calories or so above BMR and work hard and smart when you get to the gym.
Don't waste time with too much isolation work, and at least put in the big five compounds: Squats/Deads/Bench/Military Press/Weighted chins, complement these with weighted dips, alternated or not and maybe some clean and presses also alternated, and you will surprise your self.
However...give it at least two full cycles before you show some sizeable gains, and oh yeah...eat like its your job!