Uprising, I don't know if anyone has addressed this to you yet, because I just skipped all of the other posts. But, to me it just sounds like you have a very fast metabolism, naturally that is... it's the case for alot of people that are smokers, who drink alot of caffeine (seriously, lay off the caffeine, you will feel much, much better if you quit coffee, or tea, or all that nasty shit, if you want a good substitute for tea or coffee, go with Chinese herbal tea, or chamomile) and who use stimulants like mdma, coke or methamphetamine in their spare time. Combine all of your vice of choice, with your naturally fast metabolism, then you possibly have a pretty fast bpm at rest.
Imagine what it reaches when you're active!
I can't emphasize this more, but if you want to gain weight, then you are going to have to completely lay off any form of stimulant. Sure, it's ok, maybe once or twice a year for a treat or special occasion, but no tweaker, or cokehead is going to gain a significant amount of muscle, or even fat by hitting the pipe every 2 days. Unfortunately, it just doesn't work like that.
Stimulant-type drugs, are by far the worst for you, if you are looking at gaining. Not to mention, extremely bad for your well-being and your heart for when you are active and doing cardio, or general lifting.
Alcohol as well. I wouldn't recommend using this shit. You can, again, occasionally, but it's obviously a better idea to steer clear. That shit will degenerate your muscle quicker than you can imagine and it tends to make you put weight on in places you don't want it to be, like your gut, or your big toe.
I'm sure others have said this. But, eating good for only a month is not going to make you gain a significant amount either. It has to be a consistant thing, for many, many months before someone like you (or me) with a fast metabolism sees any significant weight (muscle, or otherwise) gain. Keep your diets balanced. Don't be fooled into thinking the more fatty and greasy foods you are going to eat, means you are going to put on weight. People tend to generally think like this naturally though.
Sure, for some people, eating donuts and McDonald's every day is going to make them gain some kilos, but it doesn't seem to be the case for all of us. I have no idea why this is.
Eat lots of fish (really, this is one of the best ime), when I say fish, I don't mean like tiny amounts either, I mean REAL fish! Stuff like Swordfish steaks, Marlin, Fresh Tuna steaks (not the fake canned shit either). These sort of fish contain alot of natural oils. You need this.
Decently sized steaks like lean eye fillet (not scotch fillet, because it tends to contain marlble in it, whicn is basically alot of fat mixed throughout the meat), Porterhouse steak (with the fat cut off), etc...
Vegetables. Lots of vegetable soup, mixed with broad beans, and other types of beans. Buck Choy, other Chinese greens are good, Spinach, etc...
Water and Milk, drink loads of it. Plain (not skim milk) milk is one of my most favourite beverages. Seriously, very refreshing and is good for gaining weight too.
Cut down on the cardio. Don't over exert yourself, don't do cardio that isn't necessary. I am of the opinion that if you walk at least 2 kilometres a day, then you have no need for cardio... I could be wrong though.
Anyways, good luck. How's it all going anyways?