Are you in a local guilting group? Do you have a LQS nearby? You might want to ask someone watch you as you cut. They may be able to give you some pointers on what you may be doing wrong and tips to make cutting easier.
Does your rotary cutter have a new blade? Do you have a handle attached to your ruler? What size ruler are you using? Are you using a ruler to cut by or the lines on the cutting mat? Generally I never use the lines on the cutting mat but always use a ruler for measurements. It is also recommended to use the same brand of rulers or only one ruler per project for fabric measurement for cutting? Are you cutting strips that are too long? How many layers are you trying to cut through? Have you tried putting grippers on the bottom of your ruler? If budget is a problem, try several pieces of double sided tape. This will help to keep the ruler from slipping on the fabric. Have you washed the fabric before cutting? If you have washed the fabric have you ironed and starched the fabric? Did you use starch or sizing or Best Press? Are you cutting at an angle or straight in front of your body? What is the height of your cutting surface? Is the cutting surface too low or too high? Is your cutting mat clean? Is your cutting mat moving while you're cutting? What size rotary cutter are you using? Are you able to grip the cutter properly?
Have you checkout out videos on You Tube? You might to watch as others are cutting fabric to see their method. Are you cutting with the same method?
I know many questions. I would seek out another quilter or group and see if you can get some personal hand's on assistance with your cutting skills.
Keep us updated on your situation and progress.
Pam M