I'm a little confused about the actual problem. Is it maintaining a steady rhythm or figuring out the duration of the individual notes within a measure? Or both?
If it's the duration, then counting of some form is the only way I can figure it out. Especially with those pesky dotted notes. This is often done measure by measure or phrase by phrase. As the "inner ear" (the one in your brain) begins to "hear" the way the measure/phrase is supposed to sound, fitting it into the overall rhythm of the piece becomes easier.
If it's steady rhythm, then a metronome can help a great deal, as frustrating as they can be. What I found was that playing with a metronome is a skill unto itself. If you're not used to one, play drills or scales, or pieces you know really well with the metronome first. Aim at tempos that feel natural for what you're playing at first. Speed up or slow down as you get better. I found playing slow harder than playing fast.
There's one in every crowd.