After I get up from laying down for a long time...?

So if I'm laying down for a while and then get up and walk a few feet I het really dizzy and I litterally like can't see like I kinda black outish but I can still see little peaces of my vision. I can also see random blue dots. This only last for like 10 seconds but should I be concerned? It used to happen a lot less like 2-3 times a week but 6 weeks ago I got a concussion and it has been happening around 5 times a week. I'm 14. What could be wrong and what should I do? Thanks you.