First off - I would strongly encourage you to talk to your Bishop about this. You haven't committed sin - from what I can tell - but questions like this are what Bishops are for. This will be a good opportunity for you and your Bishop to have a good discussion about this. Having a good relationship with your Bishop will help you over the long run. Hopefully you feel comfortable in talking to your Bishop. Bishops greatly appreciate people coming to them asking for help before they have gone too far. He will help you and will be a great source of strength for you. 
 
Also - remember to consult with the For Strength of the Youth pamphlet.  
 
Just my thoughts: Simply kissing is not necessarily a sin by itself, but what it may lead to can be sinful. 
 
A short, good-bye kiss is probably ok. But what you will find is that the more you kiss - the more you will want to kiss and the higher chance it will lead to something more. Kissing is kind of like the story of the camel in the desert. Here is the story: 
 
There is an old Arabian story ....  
Once upon a time long ago (a good start to any story) a Sheik had to travel to a far distant city across a scorching desert....and so it came to pass that the sheik set out on his journey, however deserts being treacherous places he encountered a fierce howling sand storm...the sheik thought that it would be prudent to take shelter, promptly set up his tent and took shelter from the raging storm with his camel tethered outside....after a little while sitting there sheltered from the storm the sheik heard a voice from outside the tent...it was his camel (all animals can talk in all fables worthy of the name)..."Oh kind and generous master. Sir, the wind is so harsh and the sand relentlessly lashes me raw...may I just shelter my nose and mouth from the storm just inside the entrance way to your tent?"  
The Sheik was touched by the humble nature of his faithful camel's request and thought to himself..."Indeed my camel ,my faithful servant, has borne me on his back without complaint through the scorching dry desert and surely deserves some respite from this terrible storm" and with this allowed the camel to place his nose and mouth just inside the entranceway to the tent....  
A little more time passed........  
and again the camel spoke..."Oh Kind and Merciful Master, thank you for so generously affording me the shelter of your tent for my mouth and nose that they might be given relief from the storm....is it possible that i might also shelter my eyes from the stinging burning sands?"  
and so the sheik once again granted the camel his request.  
After a short while the camel spoke yet again..."Oh Wonderous,merciful....."  
To cut a long story short...the sheik soon found himself outside in the violent sandstorm and wondering how it was that he was outside and the camel in his tent.  
The answer of course is that humble requests for simple small favors are hard to deny...and it brought about gradual small change in the situation that a larger change was effected.  
 
Kissing is like the camel. Initially a few kisses can eventually lead to bigger, more sinful things. I would recommend putting a definite limit (maybe just a couple of kisses - or maybe no kisses) and then sticking to that limit. Once you start expanding the number and length of kisses then you start putting yourself in a dangerous, difficult situation. I can tell that you don't want to do that. 
 
Beyond limiting the number of kisses - you can set other boundaries/limitations as well. Here are some: 
- Never lay down next to each other - body to body. 
- Never go in to a bedroom just the two of you 
- Ensure that there is never any inappropriate touching. 
- Never lay on a bed together. Remember - 4 on the floor! (4 Feet on the floor) 
- Never stay up really late together. We have always taught our kids that our curfew is strict. (Our family curfew is 11:30pm) 
 
You can come up with others. If you and your boyfriend can sit down and together identify what those boundaries (rules) are for you and you both agree to them - then each of you can help each other in keeping them. 
 
Let me reinforce that you should be having this conversation with you Bishop. He will help you determine and set the boundaries for you and your boyfriend.  
 
Good luck