Miscarriage symptoms

I had a miscarriage in October and didn’t really have any symptoms leading up to besides light cramping here and there and then of course bad cramps when I was bleeding. I’m now 7 weeks pregnant I conceived right after my miscarriage but I’ve been having lower back pain and aching in my pelvic area almost like my period is coming and I’m worried this is gonna be the start of a miscarriage even though it’s been going on for like 3 weeks and I saw a strong heartbeat on Monday. So I’m wondering if anyone had symptoms like this leading up to their miscarriage and how long those went on for?