I Think I Have Shoulder Instability But I'm Not Sure,

I think I have shoulder instability but I'm not sure, but when ever I move my left shoulder in a windmill motion it clicks in and out of place and when I sit up It feels like an aching pain in between the top of my shoulder and the top of my neck. I don't know what to do as my mum thinks it is because I am on my phone a lot but I try to lay down when ever I can but I don't know if that would help at all.