I think twice.. Once to Jonas Hanson and once to Pete Shanahan. I think that's it but I could be wrong.. At least if your talking in the main show universe.. In several other universe's and timeline's Sam was sometimes married, widowed or even divorced, but I don't remember any just plain engagements. I don't remember the amounts from those because there was so many alternate Carters lol. I think those alternate ones where usually to Jack, but also she had been with Rodney and that Ambassador guy Faxon, and possibly Martouf.