Can Fibrosis In Lungs Be Mistaken For TB?

I was diagnosed with PTB, South Africa in 1996. I took treatment for 6months and was cured. From 2005 I started working for US security companies and everytime I had to do medicals but they seem not to be happy when I tell them beforehand about this and I have been doing medical check ups and I do not have active TB but have fibrosis in my lungs. Now I am working for a different company also US, have to do medicals must I tell them about my previous diagnosis beforehand or they must find out on the X-Ray? What if they become unhappy and fire me though I am not sick? I am 35 years, 1,79m, 84kg. I have never suffered of any other illness except the above. Not drinking and not smoking and never before!