I'm 20 years old and in fairly good shape. About a month ago I chaged my diet so I could lose some weight. Started eatingn healthier and lest calories then I use to. About 2 weeks ago I noticed that I wasn't gettkng random erections anymore throughout the day. I also noticed the big vein on my penis isn't as large or shows as much. My penis also looks a lot smaller then normal. I normally mastrubate once a night to porn. So I finally saw my girlfriend of 4 years for the first time in a month and I kept losing the erection and getting it back during sex. I know it's not performance anxiety or being over excited for the sex cause I didn't even know it was going to happen. Should I go see the doctor about this?