Hi Squidipa
The pains in your tummy are caused by everything stretching and growing and is quite common.
Heavy breasts are another common problem in early pregnancy.
Gas and constipation are another normal symptom. To help with the constipation not only do you need fibre but you also need fluids. I recommend drinking between 2 and 3 litres of water a day. If this does not help get some coloxyl and senna tablets from the chemist. Start with 1 tablet twice a day for 3 days. If this does not work take 2 tablets in the morning and 1 tablet at night.
The out of breath thing is a little unusual and could indicate that you are low in iron. I suggest that you talk to your doctor about this.