I am 13 and my penis is 2 and 1/4 inches. Is that average? Also I can precum and when I ejaculate I feel a tingly sensation in my stomach. Does that mean I'm going to ejaculate? I stop because I'm scared when it happens.
A growing penis can be any size during its growth. There is no average size for a particular age because each person grows at different times and at different rates.
I assume you meant to say "masturbate" instead of "ejaculate." Masturbate means to play with your penis to cause a desire to ejaculate. The tingling sensation is your muscles contracting for an ejaculation, but since you have not developed to the point of producing semen yet, all you get is the feeling and no result. When you do start producing semen, the feeling will be far more intense and you will also squirt out a milky-white liquid, which is semen. When you do develop to that point, there is no stopping an ejaculation once that point of a tingling feeling is reached.
Just be patient. There is no need to rush things. It will all come together when the time is proper.