If you often find yourself waiting for hours or, worse, days for a text or call, then you are not in a real relationship. If you often find yourself wondering where your partner is, not knowing if they are OK, you are not in a real relationship. If you often find yourself still wondering where you really stand, you are not in a real relationship. If your partner often flirts and entertains others, you are not in a real relationship. When you're in a real relationship, both of you are investing, not just you.
There are literally billions of people on this planet. You don't need to be wasting your time and energy on someone who doesn't even acknowledge your existence unless they need or want someone from you. So stop investing in something that is leading nowhere, something that is only gonna end in you getting hurt. Don’t be someone’s option or placeholder. Move on and find someone who wants what you want, and more importantly, someone who wants you just as you want them. That person is out there. Don't give up.