Hey man, it's all good. Fighting/Sparring is not a natural act by any means. Adrenaline levels are up, heart is racing...If you can get yourself to relax the tense muscles and BREATHE.

For me my biggest issues are relaxing my shoulders and arms, but when you see punches coming it's only natural to cover with flexed muscles. The more you get in the ring and spar, the more comfortable you will be come. It's when you start reacting out of instinct, rather than having to think about what you are doing, that you know you are getting comfortable and becoming a boxer.

Work that jab, keep the head moving, footwork, breathe, try to relax and have fun. Combos won't always land. Pump the jab, put a right hand behind it, evade, step to the side, pivot, circle left, circle right, jab, jab, move out. Never be stationary.

I still get nervous every time I spar, most of the guys I ask say they do too. Just try to go with it and use that energy to find your fighting style. Eventually things will start to flow. Also, keep those elbows protecting the ribs and liver when your guard is up. Shoulder endurance from the speed bag helps.

Watch other guys that spar and see how they move in the ring. What their offense strategy is like, what their weaknesses are. Watch pro boxing and mimic a fighter similar to your build.

Good luck, and stay with it!