All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
There is no harm in supplicating Allaah, The Exalted, to facilitate your marriage. We know of no specific supplication to be recited in such a case. You can recite the reported supplications for seeking the help and assistance of Allaah to facilitate one’s affairs. For instance, the Prophet, sallallaahu ‘alayhi wa sallam, said: “The supplications of a person in distress is to say, ‘Allaahumma rahmataka arjoo fala takilni ila nafsee tarfata ‘aynin, wa aslih lee sha’nee kullah (which means: O Allaah! I seek Your mercy, so do not leave me to my own self even for an instant; set right for me all my affairs. There is no god but You).” [Ahmad and Abu Daawood]
Moreover, the Prophet, sallallaahu ‘alayhi wa sallam, used to say: “Allaahumma laa sahla illaa maa ja‘altahoo sahlan, wa 'anta taj‘alul hazna ithaa shi'ta sahlan (which means: Oh Allaah! Nothing is easy except that which You have made easy. If You wish, You can make the difficult easy.)” [Ibn Hibbaan]
For more benefit, please refer to Fatwa 88282.
If this man's situation does not improve and he cannot afford to marry you, you should not wait for him. One does not usually know what is best for him. You should also implore Allaah to bless you with a better suitor. We have provided some guidelines in this regard in Fatwa 88665; please refer to it.
You are also advised to end your relationship with this man; it is impermissible for a Muslim woman to have a love affair with a man (other than her husband). By means of a strong will and resolve, it is easy to overcome such passionate love. Please refer to Fatwa 84544.
Allaah Knows best.