Hello sister ekhtee and welcome to your forum of good knowledge and sincere friendship.
I was distressed to read your situation and with the limited time i have these days, i couldn't pass yor call for help and the reward in trying to guide you to the better path.
Sister, know for sure that fornication is a serious sin in ISlam.
THe order of sins in greatness there is:
1) Blasphemy: the most abhorent
2) To kill a Muslim unjustly
3) To fornicate
i cant stress hard enough how urgent it is for you to repent and STOP the physical relationship. Such a relationship outside marriage robbs you from your self respect, self esteem, honour and diminshes your fear in Allah as your heart grows attached to sin and away from obedience. GET OUT OF THAT RELATONSHIP ------------NOW!!!!
Whether your boss is Muslim or not, in this case is not the issue with the greatness of the SIN. It makes a difference if you are seeking to marry him. A Muslim female cannot consolidate a mariage contract with a non-Muslim which leaves you also in a state of committing adultry if you chose to partner with a non-Muslim in what you might call a mariage.
As for Allah forgiving you!!!! Yes............Alla
h forgives the one who makes a sincere repent (before death) for any sin done in this life even if it is blashemy. SO u are lucky to have woken up to yourself before death hits you.
To REPENT NOW................
....you have to fulfil these 3 conditions:
1) Leave the sin immediatley
2) Regret having done the sin ( i mean reeeeally regret)
3)Make an undoubtful intension that you will never return to that sin again
Pray and ask his forgiveness. Cry and feel his torture in the grave where there will be no one to comfort you, nothing except your deeds will be there for you. If they are bad ones,,:(

:cwt Allah's torture is severe. But if your deeds are good ones :apl1 Allah's pleasures and rewards are like non that we can image in this world.
Remember your boss wont be there in your grave and he cetainly wont defend you on the day of judjement when you face you deeds and are asked about them. ON THAT DAY ITS EVERY MAN FOR HIMSELF.
If your boss really loved you,,,,, the true love kind...... he wouldn't have the heart to inflict such a sin on you. Remember that what you have between you and your boss is dispraised LUST, not true love. So dont feel any hestitation to leave. LEAVE NOW.
As for marrying another Muslim........that shouldnt be a problem when you prove your worth again in a sincere repentance. Im sure after repenting and practicing islam deeply, your past will be burried under the true faith that will shine from your face in obediane in Allah and since you left the lust of this world for the sake of Allah, HE AND ONLY HE HAS THE ABILITY TO REPLACE IT FOR YOU WITH A PURE MARRITAL BONDING.
REPENT MY DEAR ............REPENT.