Want to become pregnant. By medicines.

We have a 5 years old baby girl. Recently we planned for our 2nd issue. And that's why we intercourse each other from d9 to d19 of cycle one day interval. I have very good appeal for sex with my wife in past few years ago but now a days it is not happening. Because her breast size has got reduced and after I messaged her breast near about 15_20 minute, it become slight tighter than previous. Then we intercourse each other for almost 10 mins. 2nd point is many of times I feel tired to have a sex with her , I tried to convinced her near next morning but failed to do that.then I automatically masturbate himself before her. I pour my sperm into her vagina but she thinks I didn't pour the same only got time pass.But I seen her my penis to her . Many of the times only oral sex is possible if she felt to sleepy and stuck me on sex before making her high appeal on sex. I m taking vitamin b complex tablet daily basis at night . Pls suggest me how can I get rid of the problem by medicines.