A baby

So I've been with the same guy for almost 9 years and we have three kids together. Our youngest is almost one and I got my tubes tied after he was born. Well my boyfriend is just now telling me that he wishes I didn't get them tied. He said he tried to tell me he didn't want me to but I don't remember him telling me anything. But I've heard that women can still get pregnant with there tubes tied so I'm just wondering if I we were to try to have another baby, what's the chances it could happen. I was going to buy a ovulation test and go from there. Is there anyone else that has been threw this that could give me some advice?