Constipation is only a factor if you push too hard to go because of constipation, which can cause hemorrhoids or an anal fissure. It's an integrity of blood vessel issue, but the causes of that can be many. Once you have them, though, stool softeners and fiber are suggested so you don't have to press so hard to go so the tissue can heal.
No one knows for sure what causes hemorrhoids. Constipation, in some cases, might be a factor.
Hemorrhoids are caused by constipation usually.
See a doctor. Enemas taken regularly will just make it harder to go without them. Hemmorhoids don't cause constipation unless you try not to go to avoid the pain for a long period of time, in which case you might be able to work yourself into a state of constipation.