BF% is far to high to reap the full benefits of HGH. We need a lot more information. But I can tell you right off the bat without you having to tell us more, that you are not a candidate for HGH use when you have a 18% body fat and weigh 160 lbs. You said you have been working out hard for 2 years.....AND YOU STILL HAVE A 18% BF, 5'10, and are still ONLY 160lbs. ????
1) You either have absolutely no clue how to diet and train correctly or 2) you have some underlined medical problems. My guess is that you are not training and dieting correctly. 18% BF at 160 lbs. at 5'10 is...well,.....FAT. And someone who trained hard for 2 years would in no way have that high of a BF%.
Please read these threads about asking for advice....
Should YOU be using HGH? IMHO.....NO....or any other compound for that matter. Lear how to train and eat. Hard gainers are people who don't know how to reach realistic goals with conventional methods.