If by weak ejaculation, you mean you have a low sperm count, it could be the reason for your wife not getting pregnant. We are assuming you have gotten your sperm count checked. If not, get it done to know if that is the problem. Men with fewer than 15 million sperm per millilitre of semen are considered to have low sperm count. There are several ways of improving your sperm count like frequent sex, a healthy lifestyle, moderating alcohol consumption and quitting smoking. If these don’t help, you can try IVF. You should also ask your wife to visit the doctor to get herself checked.