 [ Symptoms ] we hear about adverse events [with vaccines] is that the same as a dangerous reaction [ Disease ] hi in weak sperm the only thing i can think of is slow moving sperm now if it was slow moving sperm i do not think they would make you pregnant if you have had 4 miscarriage is in the past 18 months it could be age related i know 35 may not sound old but it could stem from that try taken a few months off before you try again like 6 this would give your body a chance to reboot have a look at prenatal vitamins and supplements this way you can build yourself up if you smoke quit if you drink alcohol quit eat healthy foods get out and just do some simple exercises walking and swimming would be to good ones to try do hope this helps good luck