Three things:
1) Have your urologist write an order for Pelvic Floor Physical Therapy (PFPT). It is very common for postpartum women who need to regain their control after giving birth. Post-prostatectomy men need it too. You'll need up to 8 sessions, and your insurance company will likely only approve two at first, but your therapist will write a justification for six more that should be approved. There are so many exercises and even breathing techniques beyond Kegel exercises... I was amazed. And they all helped. I am now ~98% continent.
2) Part of PFPT is behavior modification. You are taught to drink 8 ounces "max" at any given time. As soon as you go to the bathroom to urinate, you immediately drink 8 ounces more of water right after, if you want...but it is suggested to keep you hydrated and flowing, but also to get you used to drinking just 8 ounces.
3) You will be told NOT to drink acidic beverages (OJ, etc.), and no sodas, and no caffeine, all of which are bladder irritants which will make your still-covering bladder pass quickly. That will be for a long while (2-3 months until your bladder calms down and heals). No pun intended, but your post-surgical bladder is "pissed off." It has been assaulted during the surgery and it no longer has the prostate sitting under it to help support it...it wants to leak anything and everything. To that end, your PFPT therapist will have you keep 24-hour daily logs of when you pee'd, when you drank, what you drank, and how much you drank, as well as how many diapers/briefs you used in a day. You'll be surprised at how much that log tells you, especially when you told yourself that the one cup of caffeinated coffee, and the 12 oz. afternoon soda, and the glass of wine or beer with dinner that made you pee more, and sooner than you thought. The log tells you the truth, and that you can't stray from the plan to drink only 8 ounces of water at a time for those 2-3 months. Your PFPT will tell you it is OK to cheat a little, but not much.
Good luck to you.