I am 21 weeks pregnant and have tender breasts. Today I noticed a small lump in my right breast-should I be worried?

See your doctor. There are many changes in the breasts during pregnancy. Breast tenderness is very common. However, if you have a new breast mass, i would see your doctor within a week. Be careful not to check the lump too often before you see your doctor as breast/nipple stimulation in pregnancy can cause contractions.
Yes and no. Any lump in the breast whether being pregnant or not is a matter of concern until it is confirmed that it is benign. I would suggest that you definitely have it checked. Majority of lumps are benign (non cancerous), but breast cancer needs to be ruled out. Don't wait until the end of your pregnancy to have it checked. Do it now!

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I am experiencing breast lump (quality: tender, swollen lump), rash on breast and breast pain (quality: tenderness). Symptoms started sat rashshrunk

Breast evaluation. New breast lumps should always be evaluated by a doctor. At age 16 it is highly unlikely that this is a cancerous condition. You can schedule a visit to have an exam. Breast cysts or fibrocystic changes are possible causes. Weight changes, diet, caffeine intake, ill fitting bras are all causes. The rash could indicate an infection. Read more...
Evaluation. You should see your doctor to be evaluated and have ultrasound to find the cause so be treated. Read more...