Your technique is fine and the sensations are common. You're going in the right direction. The next two things to think about is timing and letting yourself fall asleep.

(Aside: Some will say you don't need sleep paralysis to WILD. In fact, "sleep paralysis" isn't the best word to describe what you and many others experience with this technique. I really wish we called it "hypnogogic atonia" or something like that. Regardless of the choice of words, and remembering that these sensations aren't necessary for WILD, they are very common especially when you're first practicing so I think they do indicate good progress.)

So for timing, you didn't say exactly when during the night you are trying this. The standard advice is don't try this when you first go to bed because you need to be near a REM period. Try it after 4-6 hours of sleep. Ideally, you wake up naturally after a non-lucid dream in that time frame, journal that dream, and then attempt WILD. Personally, I think there's another sweet spot after 8+ hours of sleep if your body is able to sleep that long (try it on a lazy weekend when you have time to sleep in and can block sound and sunlight). You can also set an alarm if you don't wake up naturally. If using an alarm, try a gentle one that uses vibration or gradually increasing volume. There's many phone apps that do that.

Now for letting yourself fall asleep, this is the part that people have the most difficulty with. It's good that you are able get to the hypnogogic state where you start to get the sensations and hallucinations, but you must not focus too hard. Counting your breaths is a good way to relax and get to that state, but I think you want to transition to a lighter focus when you're getting closer to sleep. There's a delicate balance between staying awake and letting go into sleep, and it just takes practice and experimentation. Many people develop their own style and if you search DreamViews for WILD techniques and anchors, you will find many experienced WILDers have shared their thoughts. The first thing is to remain calm when the sensations start. It may startle you the first few times, but soon they will become familiar. When you feel them, return to your breath and welcome the sensations in. Then I like to use a visualization to ease into the dream state. I imagine the sensation of falling through the bed, which is how I typically enter WILD. Others levitate off the bed or enter a tunnel. Let your mind wander a bit and periodically return gently to imagining the visualized scene or sensation until it happens and bang, you're in the dream. But that's just my method, look for others with WILD anchors to find something that makes sense to you.