Hi there
I too was told with my first pregnancy that I too had a low lying placenta and needed an extra scan at 34 weeks to check it had moved. Like you I wasn't sure what this really meant, but my midwife reassured me that in about 1 in 4 pregnancies women have low lying placenta's, but due to the fact your uterus grows this usually pulls the placenta up and out the way by 34 weeks.
I had my scan at 34 weeks and it had moved and apparently its only 0.5% of people whose placenta's do not move in safe time for delivery.
So when pregnant with my 2nd child and again told at 20weeks I have a low placenta I thought nothing of it and went about day to day life as normal.
However, I have had complications this time. I started bleeding bright red loss at 26 weeks. I being my calm self thought it was nothing and when it was only a small loss and it stopped as quick as it came I told my midwife who checked me over and said if I bled again I had to call my labour ward.
Sadly 2 days later I bled again, but more this time, so called the hospital who told me to go straight in. They scanned me and my placenta was completely covering my cervix. They explained to me then that the risk was a massive bleed which could occur at anytime and baby would have to be born by emergency section.
The Dr here is very cautious and apparently takes no risks with women with placenta previa hence I was admitted and that was 11days ago. The bleeding stopped and has not occurred again for more than a week now.
It is so hard not being home when I have a 2yr old son that I've never been apart from for more than a day, especially when he got chicken pox last week and that's the first time he's ever been ill. BUT I know that I'm in the best place and they are taking amazing care of me.
I have a scan on Monday to check everything but am mindful that I will be here now til baby is born that might be tomorrow and it might be 10 weeks away.
If I were you I would not worry unnecessarily, the odds are so good that the placenta will move and unless you have complications otherwise then you should be able to relax.
Hope this has helped as I have only recently joined to seek advice and help from people alike