Wifi issues - broken antenna?

Recently my Wifi connection has suffered greatly on my MacBook Pro mid2012 non-retina. I now need a much stronger Wifi signal to have a working connection. I did not change my position at my desk (home and office) nor the router hardware.

The plastic clutch cover had a small crack for 2 years already (on the antenna connector side). But now I suspect that the antenna may have broke. It seems that when I press on the crack reception gets better for a while. Is there a way to sort that out? I was thinking one could, for instance, measure the electrical resistance of the antenna connectors. Any ideas?

If it should really be the antenna where could I get a replacement?

Thanks!

UPDATE:

It is the antenna - or rather the antenna cable.

Any ideas where I could get these cables?