Its your uterus contracting, when you have an orgasm thats what happens and because your uterus is growing with bub in it when it contracts it gets hard and you can feel it, baby is usually safe druing sex as the amniotic fluid protcts it, just as long as its not rough or extremely vigorus, you should be fine
Lump where? & howd u know ur pregnant? If so how far along are u? Explain more
Where is this lump? Sex during pregnancy will not hurt the baby. It's protected by amnioticfluid, cervix, and mucus plug. As long as your not spotting and your doctor hasn't specifically advised against it you should be ok.