Is it normal to spot old blood?

I am 6+3 weeks pregnant with my second child, and a few weeks ago I spotted old blood for a day then it stopped, and yesterday its started again for a few hours. I mean I have had twinges and things but my doctor ures me its normal to get aches and pains because its the baby getting comfortable etc but Im so worried. Before my daughter I had a missed miscarriage so I am petrified it could be happening again. I know it could be nothing but I cant help but worry :(