I'm 18 years old I have under arm hair chest hair, my voice has gone deeper and all that but I still don't think I have had a proper erection. But have?

Get seen. With all the images that are available, every teen knows what an erection looks like. If this is basically not happening to you, and you're not getting something that you would be able to use with a partner, you need to be seen by a urologist now. You may have a vascular defect.
Erections. Proper is a subjective thing. Healthy males and females both get erections starting in infancy.