Over Thinking Thoughts...

It's really hard for me to express myself through communication in some moments. I have a hard time gathering my thoughts and saying what's on my mind,which is usually how I feel about something or my opinions on certain topics rather it be between friends, in class, or just in a general conversation. I cannot explain the feeling of not being able to be my full self because I really feel like this is holding me back. I am a smart and beautiful individual, so what's the problem? I am on a journey to find myself ( my discovery) but I feel like this is a struggle I cannot seem to get under control. This becomes very upsetting because people do not really know what I'm feeling like on the inside. I am a very nice person like I'm always saying.. But that gives me no excuse to let people say or do what they want. I can say I have changed a lot with being too nice but I'm don't feel my full self if I can't communicate that. And maybe I'm scared but this is probrobly why I should at myself free. Font get me wrong, nobody is bossing me around or thinking they have something power over me.. It's just me not knowing what to say at any giving time about any topic that's at hand . This makes me feel really sad because sometimes I feel like I can't keep up with a conversation or my mind drifts or I'm just not intelligent enough to talk about the subject at hand. IDK.. I just been feeling like this lately. But am I the only one that feels like this... Any suggestions????