Erectile problem questions?

A few months ago I was put on an antibiotic (Bactrum, a sulfur antibiotic) and afterwards its seems like I started having erection problems. This was back in February and the symptoms are still kind of present. I can get an erection but it doesn't feel as "full" as it did prior. Also, around the time that happened, I was using a lotion that contain menthol (Vaseline Cooling Lotion) down there, if you know what I mean. I was wondering, out of the two of these situations (if not both), what could be causing my situation? I've also been stressed out lately, and I know that could have something to do with it, but it doesn't seem like that is the MAIN cause though.