totally normal.
I had this, when I abstained from PMO once. I always edged, though.....
Usually semen gets resorbed by your body if not needed. It however can happen that space becomes limited -> resulting in a wet dream. The yellow color has two reasons:
density of spermatocytes compared to the other seminal fluids.
Dead Spermatozotes resulting in higher proteine density.
There simply is no scientific evidence, that self- or external induced orgasms are necessary to mantain health. So it is not harmful. Orgasms however CAN improve many things. It is healthy to have orgasms but not unhealthy not to have them.
If necessary the body knows what to do. However, the quality of orgasm is the important factor. If an orgasm is reached under stressful circumstances it might have a worsening result.
If achieved under relaxing circumstances, the hormone-release (dopamine and oxitocyne) is higher.
The simplest way to check this is to try it. go 30 Days without Orgasm - nothing bad will happen except your orgasm being more intense.