There are many reasons for these symptoms. You may have a chest infection which is chronic rather than acute. You may have entrapment of your intercostal muscles (those between your ribs - this is not uncommon in women who have a short body - does this apply to you).
I am bit concerned about the feeling very tired and very thirsty as these can be symptoms of diabetes - do you pee excessively and have any risk factors for diabetes in which case you should have been tested for abnormalities of blood sugar. Also, although again it is normal to feel tired in pregnancy, excessive tiredness can be caused by anaemia. How long ago did you have your red blood cells checked.
It is very common to feel a bit short of breath in later pregnancy, and to feel that you have to breathe a bit faster due to the demands of the baby and also the compression of your lungs by the growing fetus.
I really think that you should run these symptoms by your Midwife for starters. No Midwife should ever think that you are wasting her time with what can appear to a woman to be trivial symtoms, you know your own body and clearly you are concerned enough about how you feel to ask the questions. I hope that your Midwife will listen to you as an old saying goes - listen to the patient - they are telling you the diagnosis. Please let us know how you get on