Boyfriend came out as bisexual and I am not sure what to think or do?

I have been with him for about 4 years now. Lately things have been going a lot better as we have had our ups and downs like a lot of relationships. We having been talking about getting married and things like that.
The day we were talking and he said he would like to try sleeping with a man to see what its like but wants me involved. I was surprised and asked so you are bi? He said yes is that problem? I said no as didn't want to seem rude or anything but truth is I am still shocked by this. He said It doesn't change things with us as he is mainly straight... I don't really understand this.
I love him so much but not sure if I should just let him go and explore on his own. A week ago we were planning the future and now I am thinking of ending things and he has no idea. I feel so guilty about this. What should I do?

He is bi and it is no big deal.
Dont let him go..it doesnt change things between you two.

IF you are unsure take a break and see how things work out.
If you two are meant to be then you will end up with him.