Hello I Am Recently Married 28 Male , Before Marriage

Hello I am recently married 28 male , before marriage I have done sex with so many married women,now I am facing difficulty with my own wife she have a tight pussy and am struggling from5 months , but now almost we are doing it but now the issue is mine penis is not that strong as before , can I use some viagra for the penitration so that we can get children , if there is any side effect in using viagra