Im 16 & Had Unprotected Sex 3 Days In A Row , We Used The Pull Out Method. My Period Is 4 Days Late I Feel A lot Of Wetness Down There But No Period. Slight Lower Back Pain & Slight Cramping And A Little Pain On The Right Side Of My Stomach . Very Irritated & All That's Coming Is Clear Watery Discharge & There's No Stress , Please HELP !

What Could Be Wrong ?

At 16 you are going to have late periods, wetness, pain in your back and pelvis, the works. Cramps are common, especially when you are late. And 'late' isn't really meaninful anyway until many more days have gone by.
That being said, of course you could be pregnant.
The words 'unprotected sex' and 'pullout method' are mutually exclusive. The failure rate of that non-method is close to 30%. Semen can dribble out and neither of you will know.
Get the pill or patch, and buy some test kits to start using soon. You may need several or just wait a little longer to start testing.

Well, you very well might be pregnant... you really didn't take any real precautions to prevent it. No condom, and no Pill is effectively no precautions. You are going to have to wait a bit and see if either your period comes... or in a few weeks take a home pregnancy test to find out for sure.

You are aware we have prominent members here, who despite using THREE forms of birth control correctly still got pregnant unexpectedly.

In fact (according to Planned Parenthood) the diagphragm, condom, withdrawal, and sponge all have the same failure rate of 15 - 24%. I had read 29% for withdrawal and condom on another site but didn't bookmark it. Obviously it is difficult to get accurate statistical data on this. Leaks can be tiny pinholes, and reporting can be wrong, and so on.

I will go further, pull out is not a method in my opinion. It is based on the boy first being able or willing to pull out, and do it on time, But at best that only lowers the amount of sperm, since there is plenty of sperm in the early fluids.

After that, if he again inserts, he will increase the chances.

So yes you can very well be pregnant, I will assume perhaps you were trying to, since you are not using any form of birth control.

At this point, you have to wait and see. And after date of period, use a home pregnancy test if you are late