It can absolutely be from anxiety. You have a big nerve that runs the whole length of your torso called the vagus nerve, and most of your internal organs connect to it. Anxiety and stress have a nasty habit of making that nerve go a little haywire and making it feel like there's sensation in parts of your body. Pressure is a very common feeling. There's nothing actually happening in your stomach, but the nerves that make it feel like there is are firing off. It's similar to an anxiety attack. In that case the nerves that feel pressure around the heart and lungs go nuts and some people say it feels like a heart attack.
The thing to remember is that if it is in fact anxiety, as is very likely since that feeling of pressure is often associated with it, there is nothing actually wrong with your stomach, it's all in the nerve. It's nothing to be alarmed about. Try some relaxation techniques, or take a warm bath, or do something to help relieve your anxiety. It should help the feeling of pressure to go away.