Get in touch with a speech therapist and start working on this immediately. Since it is a relatively new phenomenon for you, it is very much solvable with little work on your part. However if you do nothing but worry about it, the anxiety and stutter will grow by forging progressively stronger neural pathways in your brain, as it is self-enforcing. Some people have a genetic predisposition and just fall into this bad speech pattern, some get it from traumatic events like I got mine from a dog attack back when I was a toddler. Be open about your stutter with others, there's no shame in it and people will look up to you if you are honest about your struggle. Just don't feel sorry for yourself, work on it, and everything will be fine!