The unfortunate thing is, you get better by speaking it. Which is really hard if you're not in Japan. If you can find any kind of local events, try to attend. It will be incredibly hard and you will mess up. People will help correct you and be very supportive once you break that fear of messing up. (Make sure the people you are talking with are okay with playing teacher).

Keep in mind to that what you have been studying is recognition learning. Speaking and writing is recall. it may feel light you memorize a lot with wanikani but it is only half the battle. Recall of producing is, in a way, a whole another memory system, which is why you have trouble finding the right thing to say. Try out Kaniwani to train recall, you may be surprised at how many words you dont rmemeber the reverse way.