She married her boyfriend and is living a miserable life with him

The story you tell in your question in and of itself offers a
serious lesson to every girl who follows her whims and desires, fails to
obey Allaah and leaves her family and her home in order to commit sin in an
atmosphere of fitnah. Your question also offers a lesson to every sinner, to
look at the consequences to which their sin may lead them. We ask Allaah to
forgive us, you and every Muslim man and woman. 

With regard to the marriage contract between you and him, if
it was not done in the presence of your guardian and with his approval –
which is what seems to be the case – then it is not valid, and it is haraam
for you to stay with him in this case or to let him be intimate with you,
because he is not your husband. The Prophet (peace and blessings of
Allaah be upon him) said, “There is no marriage (nikaah) without a guardian
(wali).” And he (peace and blessings of Allaah be upon him) said: “Any
woman who gets married without the permission of her guardian, her marriage
is invalid, her marriage is invalid, her marriage is invalid.” 

I advise you to do a number of things: 

1 – You must ask him to put this matter right, by making a
new marriage contract with you, with a mahr (dowry) and the presence of your
guardian and two witnesses. From what you say it seems that your family now
approve of your marriage to him. So there is nothing to prevent you putting
this haraam situation right. If that is not done then he is not your
husband, and it is haraam for you to stay with him. 

2 – I advise you to be patient and to seek reward with Allaah
for the difficulties and stress that you are facing. For these difficulties
will be an expiation for your previous sins. The Prophet (peace and
blessings of Allaah be upon him) said: “No worry or grief befalls a
believer, not even a thorn that pricks him, but Allaah will expiate thereby
some of his sins.” Your patience will end in a way out, in sha Allah. As the
Prophet (peace and blessings of Allaah be upon him) said: “The way out
comes with patience.” 

3 – Note that unpleasant things only happen to people because
of their sins. Allaah says (interpretation of the meaning): 

“And whatever of misfortune befalls you, it is because of
what your hands have earned. And He pardons much”

[al-Shoora 42:30]

The difficulties and
unhappiness that you are going through may be a punishment from Allaah for
your disobeying your family and committing this haraam action. But your
regret and putting this matter right, in sha Allaah, will be your
repentance, for the Prophet (peace and blessings of Allaah be upon him)
said: “Regret is repentance.” I hope that Allaah will take away from you, as
a result of this repentance, the worry and distress that you are feeling. 

4 – Make a lot of du’aa’
and feel that you are in need of Allaah and have no one else to turn to.
Allaah says (interpretation of the meaning): 

“Is not He (better
than your gods) Who responds to the distressed one, when he calls on Him,
and Who removes the evil…?”[al-Naml 27:62] 

“And your Lord said:
“Invoke Me [i.e. believe in My Oneness (Islamic Monotheism) and ask Me for
anything] I will respond to your (invocation)”[Ghaafir 40:60]

If a person is helped (by
Allaah) to make du’aa’, then his prayer will be answered. Make the most of
the times and places where du’aa’ is answered, such as when prostrating,
before saying the tasleem at the end of the prayer, in the last third of the
night, and on Fridays, especially after ‘Asr prayer. 

5 – You have to advise
your husband and cooperate with him in obeying Allaah. Take him by the hand
and start a new life in which your aim is to please Allaah. May Allaah help
you both to do that which He loves and which pleases Him. And Allaah knows
best.