I take it you have never done a triathlon before?

In my untrained opinion, you need to add at least two run sessions to your weekly routine and be sure to include a rest day in there as well. You have plenty of time to train but if the run is not a strength then you need to start adding it in and make it a priority. Running 13.1 miles will be tough on you if you don't get started now building up to it. And remember to run a half marathon you'll need to have longer training runs to prepare for the race. You can do it...you just need to get started.

Good luck.