My boyfriend was perscribed Doxy 100mg for a problem he was having - we were seeing blood present in his urine and semen.Alot of blood.So the doc gave him doxy to take.Three days after taking doxy (twice a day) he started having a problem....he wasn't getting an erection! I don't know if this is also a side effect of doxy but we're both scared...freaked actually.I don't know what to do..can someone please, if they can, hepl us.