Practise your speech everyday for 10 minutes, or about 2-3 run throughs. You can start just by speaking to the mirror, then to your family members, and then to your close friends, and then shout it out when you're alone.
One thing I found when i was younger and wasn't able to speak in front of people was that I had a low self-confidence in myself. Every day, or when you remember, write down all the good things about you. Write about 5 good things you did today, whether it's walking across campus and taking care of your health to simply saying hello or nodding/smiling/acknowledging another person.