Blurry vision up close from contacts?!

I dont know if ive made the right connection but ever since ive been wearing contacts for the first time (about a month) ive noticed that my vision up close has gone weird sometimes. When i wore contacts for the first time ( i wear the ones that only last a day then you dispose of them) i noticed that up close when i look at my phone the words on black background goes a slightly doubled and blurry. When i wear contacts sometimes this fixes a bit when i blink but may come back again. Ive ignored it because my mum wears contacts and she said she experiences a similar thing with contacts. I dont wear contacts all the time either only like maybe once a week. I have never had problems with seeing things up close because ive always had problems with distance instead. But ive noticed that sometmies even without the contacts on i can look at my phone and it does the same effect. I thought maybe my vision up close is starting to get bad but it doesnt happen all of the time. Its only sometimes and sometimes its only very tiny and other times its a bit worse. Ive been getting sore/tired eyes (sometimes headaches between my eyes or at the front) as well for awhile and it seems that resting my eyes makes it better. I see the double/blurriness in the morning usually though and sometimes it goes away by night, sometimes i get the effect at night and sometimes i wont get it all day then itll come back a couple of days later. Its weird. I admit that i go on the computer alot and watch alot of tv which im trying to cut down on to see if thats the reason but i thought id check. Should i be worried its something worse? Or something to do with my contacts?

And btw im only 20. Could it be that the perscription is too strong and effecting my eyesight?