Don't upset the young man a party with friends. This will only set him against himself. Be wise and accept his direction. Remember, you are opponents, not enemies. You are a couple and need to support each other. Try to figure out exactly what he does when with friends. If he just talks, surely you can join his company. If for some reason your guy is resisting this, proceed gradually. For a start, assign a date immediately after meeting with friends or before.
Be proactive. Call yourself a young person, talk to him. Do not take a passive position, not wait for his call. Use the time that you are unable to meet, for their own interests, because you probably have your friends, Hobbies, passions. Start to do something new and turned his attention to its development.
Talk with the second half. If this is the first real relationship for your boyfriend, he may not understand what you expect from it. Now he's comfortable as well to have fun with friends, as it was before meeting you. Do not throw tantrums, and calmly explain that you are offended by such behavior that you want to spend more time together. Find out whether he is ready for a serious relationship. If not, you either have to wait for him to Mature, or to find someone who will pay you more attention as you deserve.
Think about whether your relationship is real. When your guy is interested in you, feels for you a genuine sympathy, he will spend more time with you, not with friends. If not, it might not very important to be there. Whether you want to continue to see this man crying into the pillow or is it better to find someone who can properly prioritize, you decide.