I agree with Jamie that is sounds like you are not eating enough whole foods, plant based of course.
Animal products are high in calories for small amounts of food, oils are also calorie dense and that is the joy of eating a plant based diet that you can eat large amounts of food, feel full and satisfied, feel energetic and yet not be eating too many calories. Have a banana and berries with oatmeal or whole grain cereal or whole grain toast (Ezekiel or similar) for breakfast and then incorporate lots of vegetables and sweet potatoes and beans and greens etc for your other meals. Fruit, dates etc for snacks.
Getting enough calories is important, feeling satiated is important and getting your nutriets is also important. B12 and vitD in the winter are the vitamins that we take.
Congratulations again on giving up animal products and dairy, and don't be discouraged. Watch vegan YouTubers for ideas and research. Forums like this are an amazing source of support and information and I am so happy to have found it.
good luck, Emma JC