Doubts

"I've always had" doubts of about how must I write this sentence.

I mean: I have always had doubts ... is that right?

There's also another doubt... When I want to talk about the future. For example: "when I were living in England, I'll look for a job". Is that right? I mean that one day I'll go to England and look for a job.

Thanks on in advance for your help!

PD: how can I colour the sentences? Thanks!

And concerning your another doubt:

When I go to England, I will look for a job. 

In this type of sentances the first part of the sentance (starts with when, after, if, as soon as etc.) sets a condition for the second part and may be put in past or present. If it's in present, like in our example, then the second part of the sentance, being the issue of what's going to happen based on the pre-set condition shoud be put in future (using will, shall or to be going to). First or second part is not a strict order in the sentance:

After I get home tonight, I'm gonna watch the Winter Olympics.

I will watch the Winter Olympics, after I get home tonight.

Pretty often you need to have the first (conditional) part of the sentance put in past simple. Then the 'will' in the second part is changed into 'would':

If I went to England, I would look for a job.

or

If I lived in England, I would look for a job.

Ade, I just tried to explain some grammar in a simple way. So, I'm sorry if I failed :-))

Doubts

"I've always had" doubts of how must I write this sentence.

I mean: I have always had doubts ... is that right?

You could say, "I've always had doubts about how I should write this sentence." Perhaps it would sound more natural to say, "I've never been sure how to write this sentence."

There's also another doubt... When I want to talk about the future. For example: "when I were living in England, I'll look for a job". Is that right? I mean that one day I'll go England and look for a job.

Strangely, when we're talking about possible situations in the future, we use the present tense. For example, "When I'm rich, I'll buy a new car." In your example, it's the present continuous: "When I'm living in England, I'll look for a job."

Thanks on advance for your help!

PD: how can I colour the sentences? Thanks!