And secondly, your query is not offensive. In fact, your issue is very valid.
Now let's get to your concern. I'm sorry to hear about your break-up and how it still haunts you. For some bisexual guys, they really do have plans of marrying a woman in the future. Actually that is their choice. But of all obvious reasons possible, I would love to hear my guy telling me he's breaking up with me because he has fallen out of love rather than getting married to someone just to fit in the societal norms.
Your question regarding "may patutunguhan ba ang same sex relationships?" is also a valid one. Actually, it may or it may not. The one that determines it are the partners in the relationship. This does not happen among gay couples but it happens to all couples - regardless of being gay or not. But if you are asking about "patutunguhan" in the context of getting married in the future - Filipino LGBTs are far from that as of the moment since Marriage Equality here is still far from being discussed in the halls of Congress.
I think that leaving a long-time partner just to "fit in the societal norm" is an internal struggle really. Is fitting in the societal norm greater than the mutual love you have from one another? I would rather have my long-time partner be with me, for there is my family. Family is not about having a father, mother, children type, family is about individuals loving each other and living harmoniously.
Another thing is that, when you love, be prepared to be hurt - that is part of loving. We love some, we lose some in the process. It is that unique thing that makes Love a strong emotion, so strong it both moves and breaks us. Loving makes us "human".
Don't close your door just yet. Love will find you, and when you do, cherish that moment. These moments shape us - now it is completely up to you how you will make this to your advantage - for your development.
And you don't have to feel compelled to leave the guy you love just to fit in societal norm. You won't find contentment there - you won't feel whole. There will always be that feeling of emptiness in you should you do that. And others will feel it too. You will realize that founding a "typical family" just to fit in would never be satisfying for you. And it won't cease who you are.
Continue loving, let the future worry about itself. Cross the bridge, if there is one. Should there be no bridge, use a boat, or a plane, you'll get there - don't worry.
And lastly, find within you the strength to move on. It may not be easy, but the world has much to offer. Losing one guy doesn't mean the end of the world. One day you'll thank him for coming into your life and for breaking up with you using that excuse - for you'll be stronger than before.