This is a super interesting question and one that I MAY have an answer to. There are a few different stages to an erection, so it’s possible that you’re noticing your erection at different points in time rather than “different erections.” The stages are (roughly):

• Soft/flaccid: minimal blood flow provides basic oxygen and nutrition to the cells of the penis

• Early erection: muscles relax and blood is allowed to flow into the penis

• Partial erection: the incoming blood is greater than the outflowing blood, so the penis thickens and becomes more stiff

• Full erection: the amount of blood in the penis puts so much pressure on veins that blood does not drain from the penis and the erection is “rigid”

The other part of your question is that yes, there are different “types” of erections. The three types are distinguished from each other based on situation and cause:

• Psychogenic: seeing or imagining an arousing scenario stimulates the brain to make an erection (nerve input)

• Reflexogenic: touch of genital organs causes both brain stimulation and a “reflex” in the spine

• Nocturnal: occurs during the dream stage of sleep (REM)