I would suggest making an appointment with your doctor to rule out any medical issue that may be causing this.
Erectile Dysfunction is a common problem, and can be a sign of an emotional or psychological response, for example to stress. Many people find self hypnosis helpful, as this can help to resolve and reframe any issues that may be leading to this on a subconscious level (you may not consciously be aware that you are stressed, or have another concern, for example a fear of pregnancy at this time, or a reduction in self confidence, or other issue).
Self Hypnosis and clinical hypnotherapy is very different from that which is used for entertainment. Hypnosis is just a shift in awareness, and this gentle stste of relaxation can be useful at resolving issues such as these. Our thoughts, trigger our emotions, which then lead to our physical response, however we often focus exclusively on the physical aspect of any issue, such as a headache, or neck ache, without considering the issues taht may have led up to this. Hypnotherapy helps to take a more holistic response, and can be very helpful.
As suggestions you might want to have a look at some of the self hypnosis downloads provided on www.hypnosisdownloads.com as an example, however there are many reputable providers available online. An app called Hypnosis by Joseph Clough is also helpful and includes tracks for most issues such as this.