I check some fitness related forums, and I usually meet the question “What should I do if I cannot make any abdominal exercises? Even a single repetition!” A few people even complain about abdominal pain.
First of all lets talk about the pain. If you feel that your ab muscles hurt because of the pressure, there is nothing wrong with it. That proves that those muscles work, they are stimulated. If you have pain like that just keep doing ab exercises. Increase the number of reps regularly and include harder activities. Your abdominal muscles will get used to the training and this sort of pain will pass.
Anyway, if you have pain inside your belly and it is a kind of strong one time pain as if you are stabbed, in that case you should visit your doctor. This is perhaps a sign that you have some other problems. On the other hand, it is always suggested seeing your doctor if you start a new sport.
There are can be two reasons, you do workouts that need strong abdomen that you have not got yet. The other is that your abdominal muscles are so weak. Do not worry there is a solution for both.
Firstly, do not put so much focus on abdominal exercises, but instead start doing workouts which do not work your abs directly. These can be compound exercises or any other cardio training.
These sorts of workouts will train all part of your body as well as your midsection. You will have basic strength, so you will be able to begin doing ab workouts. Below you can find some tips and workouts for beginners.
Then you can continue with a group of light, but effective core exercises such as standing ones. Standing ab exercises are effortless to perform and suitable to build basic strength before doing others on the floor. Do the mentioned workouts for 1-3 months at least 3-4 times a week and then you can begin firmer core workouts.
Another solution can be to to do some yoga ab workouts since in most of the these moves are not so hard but still strengthen the muscles of the midsection.
Overall, the answer is: start without focusing on your stomach, then do lighter exercises such as standing ones and then begin doing harder ones little by little. But the most important is: Never Give Up!