There are a few reasons why a dream journal might be a better choice than a dream notebook:
Keep in mind that you can create your own dream journal by dedicating a blank book or notebook to dream journaling, and labeling it or decorating it with that theme. It's not necessary to buy a ready-made dream journal, although many people choose to because they find a store-bought one to be more helpful or inspirational in their dream interpretation process.
Some of the most common dream symbols in dreams are teeth, houses, animals, cars and driving, phones, as well as purses, wallets, and keys (especially losing them or having them stolen). A symbol often means something different for each dreamer—according to their life situation, what that symbol means to them, and the context of the symbol in that particular dream. This is where expert interpretation services can help. Dream dictionaries can only go so far in helping interpret a dream, and they can't address every possible translation for a particular dream symbol—or the specific context and situation.
It looks most likely to me that your old boyfriend in the dream actually represents your new boyfriend. The subconscious mind may be using the well-established, very familiar appearance of your past boyfriend because of the strong "boyfriend associations" it made with him in the past. Sometimes the subconscious mind lags behind when changes happen in our lives, and it takes a while for new things to "soak in" or "filter down" into the subconscious.
The real answer is in the content of these dreams. What is happening in the dream? Do the dream events parallel real events, thoughts, or feelings that you've recently had regarding your current boyfriend? If so, the old boyfriend in the dream probably represents the new boyfriend, and the dreams have absolutely nothing to do with the old boyfriend.
If the dreams are about things that are very specific to the old boyfriend, like how you liked or disliked a certain thing he used to do or say, then the person in the dream probably represents the old boyfriend. Dreams about an ex are common when we start a new relationship, for several reasons: our subconscious mind may be reminiscing or reaching closure before moving on, or it may be comparing and contrasting the ex with the new person, or it may be that meeting the new person may be triggering memories of past significant relationships (like buying a new car might trigger memories of the last time you bought a new car).
You might consider writing a letter (one you write, but you do not send) to let your subconscious speak its mind about your past boyfriend in the dreams. It looks to me that you have things about him and your experiences with him that your subconscious mind needs to express gratitude for, and some thoughts that are rolling around in there that need to be expressed. However, there is no need to actually contact the person—just being "heard" as you write down your thoughts will be enough. When you feel you have written everything you have to say—positive, negative and otherwise—tear up the letter and get rid of it. This gives your subconscious the clear message that you are releasing those thoughts and that part of your past.