His father chose a wife for him who he does not want

After being convinced for years by my parents to marry my cousin, I
finally agreed last year and got engaged. I would however admit that I
had no special liking for her and before I took the finaldecision, I
also performed Istikharah but didnt seem to get a proper answer or
direction and remained confused. I finally thoughtthat since my
parents are happy with this marriage I would go for it. I study in
another country and after we got engaged I started talking to her on
phone and among other things got to know that she has a problem of
falling hair and due to that her hair has thinned a lot. I asked her
to visit some doctors and she has started to take medications but not
of any great help as of now. After knowing all this I am very upset
with myself and also with her although I have not told anything like
that to her that might hurt her in anyway. I really feel very upset
all the time now as you would understand that I also have some
feelings and wishes abouthow my future wife should look like. Right
now I am always in distress and feel like that this is my destiny to
marry her which cannot be changed as doing that would severly damage
the relations in our family.I don't know what to do and can't stop
thinking about this. This has now started to affect my studies also. I
can't talk about this to anyone not my parents or friends. Thinking
about this is always keeping me disturbed. I have agreed to marry her
next year after my parents told me so. I don't know what to do now or
how things would go after that. I would like to have your suggestions
and guidancein this regard.
Praise be to Allah.
Firstly:
Istikhaarah is mustahabb and is prescribed in Islam, but one does not
necessarily see a dream after it or get an answer as you described.
Rather its effects appear in the matter being made easy. If the matter
is made easyand goes ahead, this is an indication that it is good, in
sha Allah.
Secondly:
The son is not obliged to obey his parents with regard to marrying a
particular woman, but if he does that to please his parents and make
them happy, he will be rewarded for that, so longas the woman is
religiously committed andof good character.
If he gives the matter some thought and decides that the woman isnot
appropriate for him, and is afraid that he will develop resentment
towards her or that he will later be forced to divorce her, then it is
better for him to tell his parents frankly about what he feels and to
apologise to them for cancelling his engagement. This is better than
going ahead with something he does not really want.
We advise you to think long and hard and to examine your fiancée's
characteristics, both positive and negative, before taking the
decisionto cancel the engagement. If she is religiously committed
andof good character, and hasno faults other than what you mention
about her hair, then this can be dealt with. And a woman may be
beautiful or acceptable despite that problem.
But we also think that you should delay going ahead with the marriage
until you have put your mind at rest about that decision.
You should offer a lot of du'aa' (supplication) and ask Allah to guide
you to that which is best in this world and in the Hereafter.

And Allah knows best.