If you are having cleanings every two months by a periodontist, you have had or still have periodontal disease and the most likely reason your tooth is loose is from bone loss.
If there simply isn't enough bone left to hold the tooth in place about the only solution to keeping the tooth is to have a bone graft, but these only work in specific areas of the mouth and for certain types of bone loss. Even if this tooth is a good candidate for grafting, you would have to act now in order to have the area stable before you go on your cruise.
Sometimes we can splint the tooth to the adjacent teeth, essentially gluing it to it's partners, but this only works if you have a natural tooth and yours is crowned, so that makes things more difficult.
Another option, if your dentist thinks there is enough bone left, is to splint this tooth to its adjacent partners by crowning it and its partners together. That is, remove the existing crown, prepare the adjacent teeth for crowns and have all three crowns fused together and cemented as a unit. This is rather expensive however.
These are about the only ways to save a periodontally compromised tooth.
I hope this answers your question. If you would like to discuss this further or have any additional questions, please reply to my answer and I will get right back to you.
Sincerely, XXXXX XXXXX DDS