Yes, you got involved with him, yes you knew he had a kid etc., However, what you did not know was that whenever his child cried he would leave you to go to the child. You did not know that there was a possibility that because of his child the BM might just manipulate him. No woman likes to sit back and watch another woman pull her man's strings.

You're not bad, you're just human. Really think about what it is that is upsetting you, is it the child, or the fact that mum called and dad went running. I suspect it is the latter and that is why you are upset. Human nature.

Now before you continue on in the relationship ask yourself a couple of questions. Does mom make a habbit of doing this, had the child been treated medically and therefore there was no medical emergency, just the kid feeling a wee bit sore and sorry for himself and could dad have spoken to him over the phone. If dad had been at work when the call came through, would he have handled it on the phone or would he have left work to go over to see him. Because if dad is the type to drop everything and run to this child, that is going to be your life now. If it wasn't important enough for him to left work for, but it was okay to leave you, then you have another problem, and that is something that you may not want to live with.

When you work out what the pattern is, then you need to ask yourself if you want to live like this forever, because it doesn't end when they grow up. There will always be something, concerts, graduations, engagements, weddings, babies....and then you start all over again with the grandchildren.

From your post I am assuming you do not have any children of your own. If you do decide to stay and have children with him, his children are not going to go away. So, BM will think her child with him takes priority, you will think your child has priority, and he if he is like most men will get caught in the middle, because he will feel guilty about the child whose mother he left.

Second marriages where children are involved are very, very hard. So, my advice to you is this. Nip this and the feelings you are having in the bud, right now. Sit down with your SO and discuss your feelings, but be clear what those feelings are yourself, if they are jealousy say so, don't blame his child because you will not win. You need to discuss all the what if's and what your expectations of your SO are, you both need to be clear on parenting, and what you can and cannot put up with in your home, you both have to be on the same page and the time to work things out is NOW. Don't drag this on. The problem you will find if you read postings on this site is due to the fact that daddy feels guilty for leaving what he says is the child, and because of the guilt, they expect the second wife to take second place to the child. In order to keep access to the child they will do anything to keep BM happy and if you both want this relationship to work then talk to your partner. Look ahead, as I said to all the functions that you may not be welcome at and start working out now how your SO feels. It is never to early to discuss these things, but there comes a day when it is too late.

May I suggest you do some more reading on the site and see what problems may come your way in the future so that you know what you need to discuss with your partner. Good Luck I hope things work out well for you.