the first thing that you should do is to stop calling him "a brother".

LOLLLLLLLLL! thats funny.
Dear sis salam alaikum,
i apologise for loling before but it just reminded me of something else my dearest apologies,
sis, first of i know that sometimes the truth hurts every human being experiences this i myself have experienced it man many many times, to be honest too many times for my own liking, its human nature in general, but if you are not told the truth then how on earth will you realise??????
i know you said that brother mujahid was harsh and judgemental etc, but what he has said is the truth, ok sorry bro but maybe it could have been put in different working since you are very sensitive due to everything that has happened, but the fact of the matter is that you were talking to this guy and in contact with him, you knew his intentions yet you did give it the time of the day and in a way pursue it by listening to him, that in itself is something that a good muslimah does not do, (but hey no ones perfect) we make mistakes but the key of it all is to learn from it and never make it again.
the first time this happened to you, you could have put a full stop to it, there is no justification nor any reason or explanation for such a dirty and filthy act to take place on behlaf of this guy, i'm not gonna call him a brother cos people like that who have no respect for women should not be called brothers.
as a good and firm believeing muslimah our aim is to find a pius and firm believing righteous husband, and we should never setlle for anything less, this guy from the start through his actions has shown you what a disrespectful, guy he is, do you seriously think that words speak louder than actions? his actions are that he harrasses you indecently then his words that he wants to marry you?
come on sis, its a bit too obvious, he only sees you as a piece of meat that he wants and you want to know why he wont stop and what will make him stop, no it will not be marriage that he is seeking, it is you and the lust for you, bet you anything and i'm sorry to have to give you this example but if you were a astray woman like him, he wouldnt even bring this none sense talk of marriage up with you if you allowed him he'd have you then thats it he has got what he has wanted and he wont even want to know you no more.
but since your a muslimah and he sees that your a practising one thats why he is using talks of marriage to lure you and sweet talk you.
I dont care if this brother is God's gift to women and nor should you, yes you are right that is a very shallow way of thinking from your behalf and due to this thinking you have got yourself in a sitaution where this brother has done these things to you.
you need to open your eyes and see the truth! and i seriouslly suggest if you really are a good muslimah then you cut off all forms of contact from this guy and do anything and everything to avoid him, if it happens that you bump into him, walk off leave, if he restrains you from doing so then scream for help and make it known to him that you are no longer having it and he wil eventually get the picture.
these men think percieve and understand differently, after he did the 1st act you still gave him the time of the day i am sure you made it clear through your words and actions that it was wrong and for him not to do it again, but their way of percieveing and understanding is that yes youhave consented and yes he can do it again, so by you even picking up that call and giving him a sec to speak is your form of consent hence why it happened the 2nd time and now the third time.
so you disconnect him off through every mean and turn to Allah swt and ask for forgiveness, cos i am sorry to say sis but even if God forbid your mum gav this guy your number, and he called you, 2 wrongs never make a right nor wll or is that any justification for you to talk to a non mahram guy on the phone in such a manner specially when the intentions are not clean, by that i mean i seriously doubt you were talking to him or felt like you were talking to your own brother.
dear sister please dont talk anything i have said into pffence i have not judged you nor have any right to, we are all sinners in our own way, but our aim ad purpose of life for our own salvation is to strive hard to become pious and righteous slaves of Allah swt.by you listening to our advice here given nor is it gonna benefit us or cause us any harm, but as a member of our ummah nd as a muslim it is our duty to remind and try to guide people to the truth, so we are only fulfilling our duty, not saying things to upset you nor cause you pain cos that in itself is a sin to do so to another human being. so forgive me if i have said anything to upset you.
Ma salama.