There are a lot of reasons for this, like brushing too hard, improper flossing techniques, infection, or gum disease can cause sore and sensitive gums. Other causes unrelated to oral hygiene could include a Vitamin K deficiency, hormonal changes during pregnancy.

Does your toothbrush looks like this?
Well... this is a sure sign that you are brushing incorrectly. The issue could be a tendency to apply too much pressure while brushing. You should change your brushing habits before damage your gums or teeth enamel.
Some questions that you are probably asking yourself
1-Can you damage your gums by using a medium or hard bristles toothbrush?-Yes
2-Can you damage your gums or tongue by brushing too hard?-Yes
3-Can you damage your gums by brushing for a long time, say 1 hour or 2?-Yes
4-Can you damage your gums by brushing in the wrong direction?-Yes
5-Can you damage your gums by brushing in the wrong spot?-Yes
6-Can you damage your gums by brushing in the wrong direction?-Yes
7-Can you damage your gums by brushing with worn out bristles?-Yes
We have GOOD NEWS!
Using and mastering the Modified Bass Technique twice a day for 3 minutes after breakfast and again after dinner with a soft bristles toothbrush that is changed out for a new one every 70 days solves all of the above issues.