155 is pretty damn skinny for 20 years old. You didn't mention your height, but if it is more than like 5'7" then you have a lot of gaining to do. The good side is that at your age and your weight, when you change your diet to enough cals to actually grow and work out accordingly, you'll get steroid like growth without the need for them. If is very important that you learn how to grow and maintain muscle without using Anabolic Androgenic Steroids (AAS) at this time in your life. If you don't then all the Anabolic Androgenic Steroids (AAS) in the world won't be able to help you now or ever. Put on at least 20lbs before you consider starting a cycle. Trust me, that will come faster than you think. 3-4 month I predict if you are on point with your eating, training, and rest. That is what most guys hope for in a cycle of the same duration. So consider yourselft lucky that you are still able to gain this naturally at your age. BTW, I don't know how you expected people to react to you when your first post was against the board rules, and your subsequent posts were pissy about how anyone dare to call you out for it instead of just answering you questions without a second thought. This board is a great one, and just like most places on this earth, when you give respect you'll get it in return. That said, I didn't see much respect coming from you posts. More entitlement and frustration toward people not simply doing your bidding. Good news is an apology goes a long way, and your a bigger man for having given it. So if you have a question that requires and opinion type answer, then ask away. And in the meantime, immerse yourselft in research and learning, as this is the only way to be safe with what you are planning on doing.
P.S. spend a bit more of the time you'd normally spend researching AAS, in the diet and training section. Trust me, this info will pay off much better and quicker than even the abslolute best cycle that could be concieved.