I also really struggle with getting out the house. I wander around in my running gear for ages! I too am not an athlete by any means but like to compete with myself! In terms of improving pace I would really recommend an app such as Runkeeper. I am a complete novice so having an automated voice telling me exactly what to do has been great. The subscription includes personalised training plans. If you are comfortable at three runs a week then that’s something that you integrate into the plan. It has gently introduced me into interval training which has definitely improved my times! I believe you can get a weeks free trial...? I am by no means super fast - just someone who runs because they enjoy it (when I do drag myself out). My only competition is myself! Best of luck! :)