I'm so sorry to hear about your loss. I cannot imagine the heartache you must be going thru. There was a guy in one of my college wards that was in this situation. His fiance had been killed in a car accident and yes, he was able to be sealed to her.
This sounds like a tough decision to make. Only you can know what the right decision is. Perhaps it is one that you can think about for some time before acting upon. My guess would be that at some point you will fall in love again and want to marry. I would probably have some heartburn over marrying a guy that was already sealed to another woman. But you may find a woman who is understanding of wanting to be sealed to her also. You may want to postpone this decision until you marry and then get the blessing of your wife before doing so.
I have lived long enough to experience some tragedies of my own, and while you never forget those experiences, it is possible to be freed from the pain via the atonement. Time allows us to heal from tragedy. Maybe get a few years down the road in your life and see how you feel about it then. If you feel the same, go ahead with the sealing .... if you don't then you know all things have worked out for the best. Good luck and may your heart be healed.