The detection time of SARMS/SERMS is about 2-3 months. SARMS and SERMS are on the WADA anti doping list so you won't be able to use them.
Using a good natural testosterone booster like HCGenerate from n2bm.com is going to be your only option really.
HCGenerate is a natural herbal based testosterone booster that contains no banned substances or illegal ingredients. It won't show up on any blood doping test.