It is good that you don't judge yourself. More than erection, are you feeling attracted towards them physically, or sexually? If you got a chance, would you like to have sexual encounter with them? If you are attracted to both men and women then may be that is what your sexual orientation is. It will be good to accept it. Any sexual contact with any man or woman has to be with proper consent and using protection. Also be aware of the emotional attachment with the person you choose to get close. Many times it's the emotional disturbance associated with relationshipa that troubles more. You may masturbate as per your desire. There is no harm in doing it. Don't force yourself to do it more frequently.