Sudden Wi-Fi Strength Issues in my room (Surface Pro 2, Windows 8.1/10+ Apple iPhone 5)

Hi there. Around Friday I noticed that the wi-fi strength in my room suddenly dropped extremely low. The issue was present with both my Surface Pro 2 with Windows 8.1, and my Apple iPhone 5. The issue was not present when I tried my sister's Macbook Pro in my room, however.

The router is located downstairs. We have BT Infinity + an Apple Base Station. All other rooms in the house have 4/5 bar Wi-Fi, except for my room which is 1 bar, 2 at best and sometimes no Wi-Fi at all. This issue has come on suddenly, nothing has changed to my knowledge to cause this issue.

I updated the Surface Pro to Windows 10 today. The same issue persists. FYI I don't live in a huge mansion.

I would greatly appreciate any help anyone could give me.