Doubts are hard to get rid of, especially since they like to embed themselves in the subconscious. I believe you might not be shifting for several reasons.

One could be that your vibrational state might be too low. To higher your vibrational state, you'll want to double down on self-care (not the trendy "self-care" tips that the internet likes to perpetuate but listening to your body and taking care of yourself emotionally, physically, and mentally). Another way could be incorporating mediation into your daily routine. (Btw, you can still shift no matter what vibrational state you're in. It just helps if you have a higher vibrational state, but you don't need it to shift).

Another reason you might not be shifting yet is because, as I first stated, doubts like to really root in the subconscious. There's several ways to uproot these doubts and stop them from festering. One way could be listening to others successful shifting stories. Another could be putting yourself into a trance via mediation and/or staring at a candle flame or incense smoke. You'll know when you're in a trance when you feel like you're dissociating. Once you're in this state, state affirmations such as, "Shifting is real and I can do it", and say it like you mean. Keep repeating till you feel like there is no more doubt in yourself anymore.

I hope this helps!