Where were the children born? You were in BC, where was your girlfriend?
Is your name on the Birth Certificate?
I have some suggestions for you, I am not saying you shouldn't try to get them back, but I am saying you need to know exactly why and what you are doing and how it is REALLY going to be when you do.
I would suggest you contact a legal aid office and see what your rights are. But first you need to really think about this, and try to do it in a non-emotional way. It isn't going to be easy, but you owe it to yourself and your children to do so.
What is the mother's desire in this? Are you together, and wanting them back? Or do you want them alone?
Then you need to ask yourself some hard questions.
Do you want the babies back because you think it will mend your relationship? It won't -- having children is difficult, and it won't make things easier.
Are you finacially able to raise them? Children are expensive, three infants will be a huge stress and expense.
Are you emotionally able to raise them? Again, Children are expensive, raising them is not simple, it is tiring, and taxing and you need to be very emotionally ready to do it. One is hard, three will be even more so.
Do you have a stable home to raise them in? Same as above. You need to be set and able to look after all of you. You need to not be worrying about where you are living.
Make sure you have a real sense of what you want and why you are doing it before you carry on. I am not only an adoptee, but I am also a mother (I was just a bit younger than you when I had my first) -- so I do have feelings about both issues. Hope this helps.