There is a hadith, in which the Prophet Mohammad, peace be upon him, says:
"No one sheds tears but Allah will save his body from the fire of Hell. If the tears trickle down a person’s cheeks, his or her face will be saved from any degradation. If one out of a group of people cries, the whole group will be blessed by Allah. Only tears have unrestricted power. Verily, tears can extinguish the fire of Hell."
This shows us how wonderful it is to cry for Allah's Sake. Tears are not something that we can fake. They are the result of true and deep emotions. The Prophet says that "the Hellfire is forbidden to touch the eyes of the one who shed tears at the remembrance of Allah."
Meditate on the last part of the Hadith that I told you, on how "tears can extinguish the fire of Hell". This is how powerful your tears are!
I have read many websites, where believers (mostly men) are distraught, because they can't cry for Allah's Sake. They are aware of the Reward for tears in His Remembrance, yet as much as they try to cry, they cannot. They feel like they are "missing out" on one of Allah's Greatest Rewards.
Since you are able to cry for His Sake and you do so, even when you try to hold it back, it is a very good sign and you are very lucky. Be thankful! God bless you!