Aches and pains such as those you describe are very common during the first half of pregnancy. As the uterus (womb) grows, so the ligaments (muscles) supporting it are stretched. This can cause some discomfort – often worse when you walk, move suddenly, or cough. If this is the cause of the pain you mention, then things will get much easier as the weeks go by.
If you are further on in pregnancy then the pains may be made worse by the way the baby is lying, since he or she may be putting pressure on certain nerves. You could try lying on the opposite side at night in bed. Doing so may encourage your baby to change position and so relieve this pain.
You may also get some relief if your wear support tights, a maternity support belt, or some close-fitting cycling shorts or similar clothes.
As far as I can tell, I don’t think this is anything serious – but I do suggest you tell your midwife or doctor about the pain next time you have an antenatal check-up. Contact them more urgently if you have any other symptoms (pain passing urine, vaginal bleeding, severe backache or whatever) – or if you still feel worried. I hope you get some relief soon.