I am a male aged 51 and my partner is 40. Six months ago, she left a loveless marriage. I enjoy the sex but sometimes it can last four to five hours, and she will orgasm on average a similar number of times. I have secretly been using Viagra to help me, but I fear that if I ever say I am tired or don’t want to continue, she will be disappointed or angry.

No matter who says “no” (or “no more”) – male or female – it truly means “no” and must always be respected. It is very important to set boundaries. I am not surprised you are using medication to help; one’s ability to become, and remain, aroused can be negatively affected by the psychological effects of feeling pressured to “perform”. There are, however, a number of strategies you could try – for example, using oral or manual techniques, erotic games and role-play, or toys. It could also be worth exploring Tantric techniques, since some are well-designed to prolong erotic sessions in a less performance-oriented fashion. At the very least, have a frank conversation with her that begins with a reaffirmation of the enjoyment you experience, then progresses to explaining that there is a point during these sessions when you stop enjoying them – especially when you feel overburdened by performance pressure – and must insist on taking breaks. Let her know that at such times you need her understanding and respect.

• Pamela Stephenson Connolly is a psychotherapist who specialises in treating sexual disorders.

• If you would like advice from Pamela Stephenson Connolly on sexual matters, send us a brief description of your concerns to private.lives@theguardian.com (please don’t send attachments).