Is Sustanon Or Nolvadex Safe To Increase Weight?

hi im 23 and have always been slim after a few years of thought and and trying many different ways of bulking up i have decided to take steroids and believe me its took alot of time to come to this descision for as long as can remember i have always been 7 stone i tryed all sorts of things to gain weight and dont get me wrong i have had results i changed my diet and work out regularly i managed to get up to 8 stone and live quite a healthy lifestyle but i cant break the barrier and peolpe say eat more do this and do that and ive tryed but it is not possible for me to eat anymore i cant do it i get up have a large breakfast of all the proper foods i snack all through the day between lunch dinner another small meal and supper and nothing my doctor says im at the lower end of the weight for my height but healthy but im not happy so i am definately going to take steroids im just lookin for some advice as i know how damaging they can be i know people who take sustanon and deca and are huge even after stopping taking them remained big i know they do 8 week cycles but i am planning on taking only the sustanon 300mg a week mon/thur split as im not looking to be huge just a bit bigger but but not sure about doing a 4 or 6 week cycle? and am more concerned with the post cycle therapy was going to take nolvadex and was wondering after my cycle should i still take it and how much how often? the reason i came on this is every1 on the net has too many varied opinions and i know how dangerous this stuff can be so i want to know the safest way any hel;p would be appreciated