Ok I'm going to layout what you need to do.
At 25 years old you are a little young to be messing with roids if not genetically gifted with a REAL shot at a pro card or serious athletic career/modeling. Repeatedly using gear WILL have an effect on your HPTA and nuts when you hit your late 30's to early 40's - PCT or not. I blast and cruise now because my body at 43 does not produce test even remotely close to what it did as a natural. I went on full time around 39 years old and I likely wouldn't have needed to if I hadn't done the cycles I had in my 20's and 30's. Perils of steroid use are often overblown and exaggerated, but they are not a joke and can cause health risks if you don't know what you are doing. You should know damn near everything you would ever need to know by the time you run your first cycle (not including things you can only know from how your body personally reacts). You can learn that reading the forums going back years. I'd recommend a full year of studying the information archived here before even considering it.
Now, you don't need steroids. You are underweight for your height by a minimum of 10-15lbs - and that's for a lean runner type. I know because I'm 5'8.5" and have run the gamut from 155lbs to 248lbs. I don't know your bone structure, but 15lbs gained in two years training 3x a week is CRAP. Utter crap. I'm not saying that to be a dick, but there is something wrong with what you are doing.
First, you probably don't eat enough.
Second, you probably don't sleep enough. 7 hours a night minimum.
Third, you are probably abit of a hardgainer. 3x a week training might be a bit much for your systemic recovery ability. I would recommend training 2x a week instead of three.
Fourth, even if you go on steroids, bumping your training frequency up to 5-6x a week will almost certainly burn you out fast - if you don't train like a fluff and pump candy ass.
Fifth, you probably don't train hard enough.
I'd recommend an A and B workout split:
Monday
Barbell Full Squat 1x10-20
Weighted Dip 1x4-8
Weighted Chinups (or Curlgrip Pulldown) 1x3-8
Calf Raise 1x10-20
Thursday
Barbell Deadlift 1x8-12
Standing Barbell Press 1x6-10
Barbell Row 1x6-10
Bench Press 1x6-10
That's it. Use a 1-2 second positive rep speed, and a 4-5 second negative rep speed. Pause at the fully stretched position of each rep for 1 second. Hold the contraction on each rep for roughly a second - get a good squeeze on the muscle. Control the weight and focus on lifting it with the muscle your are trying to stimulate. Exercise form and technique can greatly vary/alter how much of the load is being pinpointed to a given muscle - upright dips vs wider grip leaning forward ha
The two primary factors for stimulating muscle growth are intensity of effort, and time under load.
Intensity of effort: taking your set to the point that you cannot complete a rep, until the bar stops moving and you can complete the positive (concentric) portion of the rep with recruit and fatigue the majority of your fast twitch muscle fibers which are the ones with the most growth potential. Failing to train a set to that level of intensity will not fatigue those fast twitch fibers enough, which will then require you to use multiple sets of the same exercise to before you fail on a rep of your 3rd,4th, or whatever final set you have ala 3 sets of 10 reps.
Time under load: Most of the damage that occurs to the muscle happens when you lower the weight. That is called the negative or eccentric part of the rep. You stimulate muscle growth when you cause metabolic stress in a muscle to occur. Typically this results in the muscle getting pumped and beginning to feel like its burning on the last few reps. You NEED slow negatives on your single sets to get your muscle under load long enough to produce that metabolic stress. A single set with a 1 second positive and 1-2 second negative on each rep for 5-8 reps will likely not result in optimal stress buildup in the muscle. You can train hard or long, but not both.
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